recipes for growing sugar crystals

7/30/2019 Recipes for Growing Sugar Crystals

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Recipes for Growing Sugar Crystals

Since I issued this website I got several requests for recipes to grow crystals, some asked

especially for recipes to grow sugar crystals.

It seems that the common recipes are only vague or not working sufficiently.One of the big problems growing crystals of sugar is its extreme high solubility and the

high viscosity of its solution.

The good thing is its available anywhere, its cheap and its not poisonous.

If we talk about sugar we mean cane sugar as there are many kinds of different "sugars"which are all separate "chemicals" like glucose, fructose, xylose, maltose etc.

Before we begin, something about units. Many of you may still be used to ounces, pounds,

Fahrenheit etc. In spite the fact that I still use this units in this script sometimes I

recommend strongly that you get used to metric units, its so much easier to calculate withthem!

If you buy scales, measuring caps etc. make sure that they have metric units, too. That

makes it easier to switch.

Physical and Crystallographical Properties

chemical names : sucrose, saccharose, beta-D-Fructofuranosyl-alpha-D-glucopyranoside

formula : C12H22O11

molar mass : 342.30

Specific gravity : 1.587

melting point : 160 - 186 C (under decomposition !)

crystal class : monoclinic spenoidal

Either known as cane sugar when made out of sugar cane or as beet sugar when made outof sugar beets. Dont be confused both are the absolute identical chemical compound.

Sugar is one of the purest commercially distributed organic "chemicals" produced inmillions of tons. There is no need to buy analytical grade sugar for crystal growing

experiments, its only something for scientists or if you have too much money. Just take the

regular sugar from the next supermarket - watch for sales (sugar cannot rot)!


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Sugar crystal floating in a saturated solution. Crystal size app.

10 mm, picture taken in polarized light

Crystal form of sugar

How to grow sugar crystals from a solution in water

There are two simple basic methods to grow crystals from a solution

The Evaporation Method

The Slowly Cooling Method

Using the evaporation method you simply let evaporate the solvent (e.g. water) of your

saturated solution to get crystals.Its quite simple but may take a long time. If the solubility is low you may have to wait a

very long time to get nicely sized crystals. Fortunately in the case of sugar the solubility is

very high.

Using the slowly cooling method you produce a hot saturated solution and let cool it downslowly to get the crystals.

The catch is let it cool down slowly. As slower a solution cools down as bigger and finer

the crystals will be. The second catch it does not work with substances which do not change

solubility greatly with rising temperature (like regular table salt) or which solubility godown with rising temperatures.(this is not very common but it happens). Fortunately the

solubility of sugar rises greatly when the temperature goes up.


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The good thing is this method is quick you will get nice sized crystals within several hours

to days.

The Evaporation Method

Dissolve per 100 gms of water 230 gms of sugar heat up the solution until it boils and getsclear. Then if you want filter use a regular coffee filter with paper, but filtering is notabsolutely necessary. The solution may have a slight yellow hue. For heating up the

solution use a cooking pot or a vessel made from heat resistant glass (Pyrex), as for

example replacement jars for electric coffee machines. You may also use the microwavebut of course only use vessels which are suitable for this (no metal or metal parts!).

To grow the crystals you can use any kind of glass or plastic container with a wide open

mouth. For example preservation glasses etc. You should produce at least about 500 ml of

solution better around 1000 ml (or a quart). For a method how to calculate a specificvolume of growing solution see the "Calculating a Solution" part down below.

After the covered solution has cooled down then after two or three days there should be

some sugar crystals at the bottom of the jar. If not, throw in some little grains of sugar. Letthe solution stay alone and covered for about a week.If you got no crystals on the bottom, yet even after throwing in some sugar grains your

solution can not be saturated and wont work.

This may happen either because you made a mistake with the amounts of water and sugarused, or your room temperature is well above 20 C (app. 70 F).

To avoid mistakes in the amounts of water and sugar used, use an electronic kitchen scale

which should have at least a resolution of 2 gm. (better 1 gm.) most can be switched from

oz./lbs. to metric, metric is easier to calculate. Also weigh the water, as its much moreaccurate than measuring the volume.

If your room temperature is well above 20 C you have to adjust the initial recipe. If you

look at the solubility table down below the solubility of sugar at 20 C is 203 gm. per 100gm. of water. In the recipe we took 230 gm. (27 gm. added as security gap). If you work for

example at a room temperature of 30 C you adjust the recipe to 250 gm. per 100 gm. of

water (again app. 30 gm. as security gap).Okay everything worked fine, there are some crystals at the bottom and the solution rested

for a week. Now pour the solution in your final freshly cleaned growing vessel. You may

filter it but its not absolutely necessary and filtering the viscose solution may take forever.

Now you need a seed crystal, usually you will find at the bottom nicely sized sugar crystalsalready suitable for this purpose or you may use a bought candy sugar crystal (thats

cheating !). Dry up the crystal with some paper towel and fix it with a slip knot to a thread

of "invisible sewing thread" which is a thin clear thread of nylon or use very thin fishing

line. Dont use regular threads made out of cotton etc. as they work like a wick and areeasily visible in the ready crystal.

Fix the thread to a piece of wood or a pencil for example so that the crystal suspends

somehow above 2 - 3 cm (about one inch) the bottom of your growing vessel but wellbelow the surface of the solution. Before doing that rinse the crystal on the thread shortly in

cold water.

The growing vessel must stay open to allow the water to evaporate but you may cover itwith a thin paper towel (most paper towels are multi-layer so you may split them) to


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prevent flies, wasps, dust etc. from falling into the solution.

As the water evaporates your seed crystal will grow.

This will not work if you are in a very humid climate or if your room temperature changes

and goes up.As evaporation goes on there may grow additional crystals on the bottom of the vessel on

the thread or on the sides. They grow on the cost of your desired main crystal. If so, pourthe solution in a freshly cleaned other vessel rinse the crystal and the thread shortly in coldwater (remove additional crystals which may have formed on the thread) and go on with

evaporation.

Fixing a seed crystal to a

thread with a slipknot

There is not enoughsolution in

this growing vessel

Additional crystals at the

bottom

grow on the cost of yourmain crystal !

The Slowly Cooling Method

If you produced the saturated solution for the evaporation method and found some crystals

at the bottom you already used the slowly cooling method to produce crystals! To get

bigger and better ones you just have to add more sugar (larger "security gap") and take care

that the solution cools down very slowly.A good basic recipe is to add 230 to 300 gm. of sugar to 100 gm. of water and to heat it up

until the solution boils and gets clear. You may filter it if you want but its not absolutelynecessary. Pour the solution in your final growing vessel and close it tightly. Take care that

the solution cools down very slowly by insulating it and also avoid any moving, shaking orvibration of the solution.

You may give the crystals a better surface to grow, a matrix, if you put in a piece of rock,

or have it suspended on a thread, or use a metal paper clip on a thread.It takes a few hours to days, depending on how much solution you take and how good your

insulation is, until the solution has cooled down to room temperature and the crystals are


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ready.

They main problems you may have with the slowly cooling method is that the solution does

not cool down slowly enough, which results in small crystals or your solution has cooled

down but there are no crystals at all!What happened? Super saturation! Your solution contains much more sugar than "allowed"

since there have not been formed any seed crystals spontaneously. If the solution isdisturbed or you throw in some little sugar grains crystallization starts immediately.Since the growing velocity of sugar crystals is small, solutions are often slightly

supersaturated when they have cooled down and so the crystals still grow a little while even

if the temperature does not change anymore. So allow the crystals some extra time.

The Trick with the Thermal Ballast

As more volume of solution you have as longer it will take to cool down. The reason is thatthe surface of your vessel is growing by power of two but your volume and so the amount

of heat energy is growing by power of three if you enlarge the dimension of your vessel.

The heat loss depends on the surface area available. To give you a simple example lets saywe have a cubic container of 1 inch, so the surface is 6 square inches and the volume onecubic inch. Now lets take a container of 10 inches size the volume will be 10*10*10 =

1000 cubic inches but the surface only 6*10*10 = 600 inches. With the small container you

have a volume/surface ratio of 1 to 6 with the big one a ratio of 10 to 6 and its a goodguess that cooling down takes ten times longer. So that was the physical principle!

However, who wants to handle gigantic amounts of solution just to grow some little

crystals? Nobody told you that all of the volume must be solution! Only a small amount of

solution and a large amount of water will have the same effect if you keep them separated.The pictures down below explain that to you. Just heat up a big cooking pot of water and

separately prepare some solution. Then put the container with the hot solution in your

cooking pot with hot boiling water. Take care that both are tightly closed. If you put yourcooking pot in a big box with insulation material, like Styrofoam, cotton, rock wool, saw

dust etc. you get a real slow cooling down of several days up to over a week. If you use an

electronic thermometer you can watch the temperature falling.

Heating up the thermal ballast and

your solution separately

Now the crystals grow in your

"cooking box".


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Calculating a Solution

You often will have the problem that you need a specific volume of solution to fill a

growing vessel efficiently. Lets take for example you want to use the slowly coolingmethod, have a 1000 ml jar and you want to have about 800 ml of solution which contains

260 gm. of sugar per 100 gm. of water.The specific gravity of sugar is 1.587,

so 260 gm. have a volume of 260/1.587 = 163.8 ml

+ the 100 gm. of water (which are almost exactly 100 ml)

you get a volume of 263.8 ml.

To fill up 800 ml you need 800/263.8= 3.03 times your basic recipe.

That is 3.03*100 gm. = 303 gm. of water and

3.03*260 gm. = 787.8 gm. of sugar.If you take 300 gm. of water and 790 gm. of sugar you will also be fine.

If you do not want to calculate by hand you can use this little calculator.

Conclusion

Following these instruction you did not only learn something about growing sugar crystals

but the basics of solution growth anyhow. The principles are the same growing othermaterials and there are more recipes to come. Please be patient and give me some time. If

you have questions or comments or you got nice results please eMail me (pics are

welcome).


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Solubility table for sugar in water

In gm. of sugar per 100 gm. of water and

ounces of sugar per pound of water

T in C 0 5 10 15 20 25 30 35 40 45 50

g/100 g 179.2 184.8 190.6 196.9 203.8 211.3 219.4 228.4 238.1 248.8 260.5

oz./lb 28.67 29.56 30.50 31.51 32.61 33.80 35.11 36.54 38.10 39.81 41.68

T in C 55 60 65 70 75 80 85 90 95 100

g/100 g 273.3 287.4 303.0 320.4 339.9 362.0 387.1 415.8 448.9 487.2

oz./lb 43.72 45.98 48.48 51.26 54.39 57.92 61.94 66.54 71.83 77.94

And here the same thing in degrees Fahrenheit!

T in F 35 40 45 50 55 60 65 70 75 80 85 90

g/100 g 181.0 184.1 187.3 190.6 194.1 197.7 201.4 205.4 209.5 213.9 218.5 223.3

oz./lbs 28.96 29.46 29.97 30.50 31.05 31.63 32.23 32.86 33.53 34.23 34.96 35.73

T in F 95 100 105 110 115 120 125 130 135 140 145 150

g/100 g 228.4 233.7 239.3 245.1 251.3 257.8 264.6 271.8 279.4 287.4 295.9 304.8

oz./lbs 36.54 37.39 38.28 39.22 40.21 41.25 42.34 43.49 44.70 45.98 47.34 48.77

T in F 155 160 165 170 175 180 185 190 195 200 205 210

g/100 g 314.4 324.5 335.4 347.0 359.4 372.7 387.1 402.6 419.3 437.4 456.9 478.2oz./lbs 50.30 51.93 53.66 55.52 57.50 59.64 61.94 64.41 67.09 69.98 73.11 76.51


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Solubility chart of sugar


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What is sugar?

The white stuff we know as sugar is

sucrose, a molecule composed of 12atoms of carbon, 22 atoms of hydrogen,and 11 atoms of oxygen (C12H22O11). Like all

compounds made from these threeelements, sugar is a carbohydrate. Itsfound naturally in most plants, butespecially in sugarcane and sugar beets

hence their names.

Sucrose is actually two simpler sugars

stuck together: fructose and glucose. Inrecipes, a little bit of acid (for example, some lemon juice or cream of tartar) will causesucrose to break down into these two components.

If you look closely at dry sugar, youll notice it comes in little cubelike shapes. These

are sugar crystals, orderly arrangements of sucrosemolecules.

What happens when you heat a sugar solution?

When you add sugar to water, the sugar crystals dissolve

and the sugar goes into solution. But you cant dissolve aninfinite amount of sugar into a fixed volume of water.

When as much sugar has been dissolved into a solution aspossible, the solution is said to be saturated.

The saturation point is different at different temperatures.

The higher the temperature, the more sugar that can beheld in solution.

When you cook up a batch of candy, you cook sugar,

water, and various other ingredients to extremely hightemperatures. At these high temperatures, the sugar

remains in solution, even though much of the water hasboiled away. But when the candy is through cooking and

begins to cool, there is more sugar in solution than is normally possible. The solution issaid to be supersaturated with sugar.

Supersaturation is an unstable state. The sugar molecules will begin to crystallize back

into a solid at the least provocation. Stirring or jostling of any kind can cause the sugar

to begin crystallizing.

Why are crystals undesirable in some candy recipesand how do you stopthem from forming?

Under a microscope, you cansee that sugar crystals arent

cubes, exactly, but oblong andslanted at both ends.

(Image courtesy of Nutrition andFood Management Dept., Oregon

State University)
http://www.exploratorium.edu/cooking/candy/sugar.htmlhttp://www.exploratorium.edu/cooking/candy/sugar.htmlhttp://www.exploratorium.edu/cooking/candy/sugar.html


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The fact that sugar solidifies into crystals is extremely

important in candy making. There are basically twocategories of candies - crystalline (candies which containcrystals in their finished form, such as fudge and

fondant), and noncrystalline, or amorphous (candieswhich do not contain crystals, such as lollipops, taffy,

and caramels). Recipe ingredients and procedures fornoncrystalline candies are specifically designed to

prevent the formation of sugar crystals, because theygive the resulting candy a grainy texture.

One way to prevent the crystallization of sucrose incandy is to make sure that there are other types of sugarusually, fructose andglucoseto get in the way. Large crystals of sucrose have a harder time forming when

molecules of fructose and glucose are around. Crystals form something like Legoslocking together, except that instead of Lego pieces, there are molecules. If some of

the molecules are a different size and shape, they wont fit together, and a crystaldoesnt form.

A simple way to get other types of sugar into the mix is to "invert" the sucrose (the

basic white sugar you know well) by adding an acid to the recipe. Acids such as lemonjuice or cream of tartar, cause sucrose to break up (or invert) into its two simplercomponents, fructose and glucose. Another way is to add a nonsucrose sugar, such as

corn syrup, which is mainly glucose. Some lollipop recipes use as much as 50% cornsyrup; this is to prevent sugar crystals from ruining the texture.

Fats in candy serve a similar purpose. Fatty ingredients such as butter help interferewith crystallizationagain, by getting in the way of the sucrose molecules that are

trying to lock together into crystals. Toffee owes its smooth texture and easy

breakability to an absence of sugar crystals, thanks to a large amount of butter in themix.

How to calculate Sugar saturation point?

Relevant answers:

What is the saturationpoint ofsugar in water?

Water at 25C will be saturated with sugar at a ratio of 100 grams of sugar to 100

grams of water.

What does saturationpoint have to do with dew point?

The dew pt. is the temperature @ which the air would become saturated if youcooled it.

Read more:

http://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_point#ixzz1XOxjgHau

Interfering agents(Image courtesy of Nutrition and Food

Management Dept., Oregon StateUniversity)
http://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_waterhttp://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_waterhttp://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_waterhttp://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_waterhttp://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_waterhttp://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_waterhttp://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_waterhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_point#ixzz1XOxjgHauhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_point#ixzz1XOxjgHauhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_point#ixzz1XOxjgHauhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_point#ixzz1XOxjgHauhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_point#ixzz1XOxjgHauhttp://wiki.answers.com/Q/What_does_saturation_point_have_to_do_with_dew_pointhttp://wiki.answers.com/Q/What_is_the_saturation_point_of_sugar_in_water


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What is the saturationpoint ofsugar in water at room temperature and at water's

boiling point?

The saturation point of sugar in room temperature is a 2 to 1 ratio and for the

saturation point of sugar in boiling water is a 1 to 1 ratio! Hope this helps :( !!!!!

What is the saturationpoint of salt?

It rises a little bit with temperature (warmer water, more salt can be added), but isbasically about 26-28%. Here is a nice chart:

http://en.wikipedia.org/wiki/File:SolubilityVsTemperature.png So,...

Read more:

http://wiki.answers.com/Q/How_to_calculate_Sugar_saturation_point#ixzz1XOxUaRA7

Water activityWater activity or aw was developed to account for the intensity with which water

associates with various non-aqueous constituents and solids. Simply stated, it is a measure

of the energy status of the water in a system. It is defined as thevapor pressureof a liquiddivided by that of pure water at the sametemperature; therefore, puredistilled waterhas a

water activity of exactly one.

As the temperature increases, aw typically increases, except in some products with

crystallinesaltorsugar.

Higher aw substances tend to support moremicroorganisms.Bacteriausually require atleast 0.91, andfungiat least 0.7. Seefermentation.

Water migrates from areas of high aw to areas of low aw. For example, ifhoney(aw 0.6) is

exposed to humid air (aw 0.7) the honey will absorb water from theair.

Formulae

Definition of aw:

where p is the vapor pressure of water in the substance, and p is the vapor pressure of purewater at the same temperature.

Alternate definition:
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where lw is theactivity coefficientof water and xw is the mole fraction of water in theaqueous fraction.

Relative humidity:

The relative humidity of air in equilibrium with a sample is called the EquilibriumRelative Humidity (ERH).[1]

Estimated mold-free shelf life in days at 21 C:

[citation needed]

Uses for water activity

Water activity is an important consideration for food product design and food safety.

Food product design

Food designers use water activity to formulate products that areshelf stable. If a product is

kept below a certain water activity, then mold growth is inhibited. This results in a longer

shelf-life.

Water activity values can also help limitmoisture migrationwithin a food product made

with differentingredients. If raisins of a higher water activity are packaged with bran flakesof a lower water activity, the water from the raisins will migrate to the bran flakes over

time, resulting in hard raisins and soggy bran flakes. Food formulators use water activity topredict how much moisture migration will affect their product.

Food safety

Water activity is used in many cases as acritical control pointforHazard Analysis andCritical Control Points(HACCP) programs. Samples of the food product are periodically

taken from the production area and tested to ensure water activity values are within a

specified range for food quality and safety. Measurements can be made in as little as fiveminutes, and are made regularly in most major food production facilities.

For many years, researchers tried to equate bacterial growth potential withmoisturecontent. They found that the values were not universal, but specific to each food product. W

J Scott in 1953 first established that it was water activity, notwater contentthat correlated

withbacterial growth. It is firmly established that growth of bacteria is inhibited at specific

water activity values. U.S.Food and Drug Administration(FDA) regulations forintermediate moisture foods are based on these values.
http://en.wikipedia.org/wiki/Activity_coefficienthttp://en.wikipedia.org/wiki/Activity_coefficienthttp://en.wikipedia.org/wiki/Activity_coefficienthttp://en.wikipedia.org/wiki/Relative_humidityhttp://en.wikipedia.org/wiki/Relative_humidityhttp://en.wikipedia.org/wiki/Water_activity#cite_note-isbn0-632-05327-5-0http://en.wikipedia.org/wiki/Water_activity#cite_note-isbn0-632-05327-5-0http://en.wikipedia.org/wiki/Water_activity#cite_note-isbn0-632-05327-5-0http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Shelf_stablehttp://en.wikipedia.org/wiki/Shelf_stablehttp://en.wikipedia.org/wiki/Shelf_stablehttp://en.wikipedia.org/w/index.php?title=Moisture_migration&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Moisture_migration&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Moisture_migration&action=edit&redlink=1http://en.wikipedia.org/wiki/Ingredientshttp://en.wikipedia.org/wiki/Ingredientshttp://en.wikipedia.org/wiki/Ingredientshttp://en.wikipedia.org/wiki/Critical_control_pointhttp://en.wikipedia.org/wiki/Critical_control_pointhttp://en.wikipedia.org/wiki/Critical_control_pointhttp://en.wikipedia.org/wiki/Hazard_Analysis_and_Critical_Control_Pointshttp://en.wikipedia.org/wiki/Hazard_Analysis_and_Critical_Control_Pointshttp://en.wikipedia.org/wiki/Hazard_Analysis_and_Critical_Control_Pointshttp://en.wikipedia.org/wiki/Hazard_Analysis_and_Critical_Control_Pointshttp://en.wikipedia.org/wiki/Moisture_contenthttp://en.wikipedia.org/wiki/Moisture_contenthttp://en.wikipedia.org/wiki/Moisture_contenthttp://en.wikipedia.org/wiki/Moisture_contenthttp://en.wikipedia.org/wiki/Water_contenthttp://en.wikipedia.org/wiki/Water_contenthttp://en.wikipedia.org/wiki/Water_contenthttp://en.wikipedia.org/wiki/Bacterial_growthhttp://en.wikipedia.org/wiki/Bacterial_growthhttp://en.wikipedia.org/wiki/Bacterial_growthhttp://en.wikipedia.org/wiki/Food_and_Drug_Administrationhttp://en.wikipedia.org/wiki/Food_and_Drug_Administrationhttp://en.wikipedia.org/wiki/Food_and_Drug_Administrationhttp://en.wikipedia.org/wiki/Food_and_Drug_Administrationhttp://en.wikipedia.org/wiki/Bacterial_growthhttp://en.wikipedia.org/wiki/Water_contenthttp://en.wikipedia.org/wiki/Moisture_contenthttp://en.wikipedia.org/wiki/Moisture_contenthttp://en.wikipedia.org/wiki/Hazard_Analysis_and_Critical_Control_Pointshttp://en.wikipedia.org/wiki/Hazard_Analysis_and_Critical_Control_Pointshttp://en.wikipedia.org/wiki/Critical_control_pointhttp://en.wikipedia.org/wiki/Ingredientshttp://en.wikipedia.org/w/index.php?title=Moisture_migration&action=edit&redlink=1http://en.wikipedia.org/wiki/Shelf_stablehttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Water_activity#cite_note-isbn0-632-05327-5-0http://en.wikipedia.org/wiki/Relative_humidityhttp://en.wikipedia.org/wiki/Activity_coefficient


13/23

Lowering the water activity of a food product should not be seen as a kill step. Studies in

powdered milkshow that viable cells can exist at much lower water activity values, but that

they will never grow. Over time, bacterial levels will decline.

Water activity measurement

Water activity values are obtained by either acapacitanceor a dew pointhygrometer.

Capacitance hygrometers

Capacitance hygrometers consist of two charged plates separated by apolymermembrane

dielectric. As the membrane adsorbs water, its ability to hold achargeincreases and the

capacitance is measured. This value is roughly proportional to the water activity as

determined by a sensor-specificcalibration.

Capacitance hygrometers are not affected by mostvolatilechemicals and can be much

smaller than other alternative sensors. They do not require cleaning, but are less accuratethandew point hygrometers(+/- .015 aw). They should have regular calibration checks andcan be affected by residual water in the polymer membrane (hysteresis).

Dew point hygrometers

Red line shows saturation
http://en.wikipedia.org/w/index.php?title=Kill_step&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Kill_step&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Kill_step&action=edit&redlink=1http://en.wikipedia.org/wiki/Powdered_milkhttp://en.wikipedia.org/wiki/Powdered_milkhttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Hygrometerhttp://en.wikipedia.org/wiki/Hygrometerhttp://en.wikipedia.org/wiki/Hygrometerhttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Polymeric_membranehttp://en.wikipedia.org/wiki/Polymeric_membranehttp://en.wikipedia.org/wiki/Polymeric_membranehttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Chargehttp://en.wikipedia.org/wiki/Chargehttp://en.wikipedia.org/wiki/Chargehttp://en.wikipedia.org/wiki/Calibrationhttp://en.wikipedia.org/wiki/Calibrationhttp://en.wikipedia.org/wiki/Calibrationhttp://en.wikipedia.org/wiki/Volatility_%28chemistry%29http://en.wikipedia.org/wiki/Volatility_%28chemistry%29http://en.wikipedia.org/wiki/Volatility_%28chemistry%29http://en.wikipedia.org/w/index.php?title=Dew_point_hygrometers&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Dew_point_hygrometers&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Dew_point_hygrometers&action=edit&redlink=1http://en.wikipedia.org/wiki/File:Relative_Humidity.pnghttp://en.wikipedia.org/wiki/File:Relative_Humidity.pnghttp://en.wikipedia.org/wiki/File:Relative_Humidity.pnghttp://en.wikipedia.org/wiki/File:Relative_Humidity.pnghttp://en.wikipedia.org/w/index.php?title=Dew_point_hygrometers&action=edit&redlink=1http://en.wikipedia.org/wiki/Volatility_%28chemistry%29http://en.wikipedia.org/wiki/Calibrationhttp://en.wikipedia.org/wiki/Chargehttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Polymeric_membranehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Hygrometerhttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Powdered_milkhttp://en.wikipedia.org/w/index.php?title=Kill_step&action=edit&redlink=1


14/23

The temperature at whichdewforms on a clean surface is directly related to thevaporpressureof the air. Dew point hygrometers work by placing a mirror over a closed sample

chamber. The mirror is cooled until the dew point temperature is measured by means of an

optical sensor. This temperature is then used to find therelative humidityof the chamberusingpsychrometriccharts.

This method is theoretically the most accurate (+/- .003 aw) and often the fastest. The

sensor requires cleaning if debris accumulates on the mirror.

Equilibration

With either method, vaporequilibriummust occur in the sample chamber. This will take

place over time or can be aided by the addition of a fan in the chamber.Thermalequilibriummust also take place unless the sample temperature is measured.

Water activity and moisture content

Water activity is related tomoisture contentin anon-linearrelationship known as amoisture sorption isotherm curve. These isotherms are substance and temperature specific.

Isotherms can be used to help predict product stability over time in different storageconditions.

Use in humidity control

There is net evaporation from a solution with a water activity greater than the relative

humidity of its surroundings. There is net absorption of water by a solution with a water

activity less than the relative humidity of its surroundings. Therefore, in an enclosed space,a solution can be used to regulate humidity.[2]

Selected aw values

Example foods

Substance aw

Distilled Water 1

Tap water 0.99

Raw meats 0.99 Milk 0.97

Juice 0.97

Salami .87

Cookedbacon < 0.85

SaturatedNaClsolution 0.75

Point at which cereal loses crunch 0.65
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15/23

Dried fruits 0.60

Typical indoor air 0.5 - 0.7

Honey 0.5 - 0.7

Driedfruit 0.5 - 0.6

aw values of microorganism inhibition

Microorganism Inhibited aw

Clostridium botulinumA, B .97

Clostridium botulinumE .97

Pseudomonas fluorescens .97

Clostridium perfringens .95

Escherichia coli .95

Salmonella .95

Vibrio cholerae .95

Bacillus cereus .93

Listeria monocytogenes .92

Bacillus subtilis .91

Staphylococcus aureus .86

Mostmolds .80

No microbial proliferation .50

Water activity is defined as the water requirements for survival or growth of

microorganisms. But water activity is not the same as the amount of water in a product. In

some cases, the water is bound to other molecules (say, Epsom salts) and isn't free forusage by the microbes. In other cases, the water is bound by humectants like sorbitol or

glycerin (anywhere from 10% to 20% will bind water). So water activity is actually a

measure of the amount of free (unbound or active) water molecules present in our products.Water activity increases or decreases with with increases or decreases in pressure and

temperature. pH also plays a role.

When we dissolve asolutelike salt or sugar into water, the amount of water available to our

beasties decreases so we say the water activity is reduced. Reduce it enough, and you've got

an environment inhospitable to microbes. If the microbes don't have enough water, they die

or go into a dormant state. (Remember the post the other day onosmosis? This is how salt

or sugar kills them!)

So, it looks like that not using a preservative in your sugar or salt scrub will work with two

disclaimers...

Disclaimer one: There are some microbes that can live in really hostile environments - like

the xerophilic fungus (0.61 to 0.99) or the osmophilic yeasts (0.65 to 0.81) - and there aresome, mostly yeasts, that will go into a dormant state waiting for water to come their way
http://en.wikipedia.org/wiki/Water_activity#cite_note-Marianski5-2http://en.wikipedia.org/wiki/Fruithttp://en.wikipedia.org/wiki/Fruithttp://en.wikipedia.org/wiki/Fruithttp://en.wikipedia.org/wiki/Clostridium_botulinumhttp://en.wikipedia.org/wiki/Clostridium_botulinumhttp://en.wikipedia.org/wiki/Clostridium_botulinumhttp://en.wikipedia.org/wiki/Clostridium_botulinumhttp://en.wikipedia.org/wiki/Pseudomonas_fluorescenshttp://en.wikipedia.org/wiki/Pseudomonas_fluorescenshttp://en.wikipedia.org/wiki/Clostridium_perfringenshttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Salmonellahttp://en.wikipedia.org/wiki/Salmonellahttp://en.wikipedia.org/wiki/Vibrio_choleraehttp://en.wikipedia.org/wiki/Bacillus_cereushttp://en.wikipedia.org/wiki/Bacillus_cereushttp://en.wikipedia.org/wiki/Listeria_monocytogeneshttp://en.wikipedia.org/wiki/Listeria_monocytogeneshttp://en.wikipedia.org/wiki/Bacillus_subtilishttp://en.wikipedia.org/wiki/Staphylococcus_aureushttp://en.wikipedia.org/wiki/Staphylococcus_aureushttp://en.wikipedia.org/wiki/Water_activity#cite_note-Marianski7-3http://en.wikipedia.org/wiki/Moldhttp://en.wikipedia.org/wiki/Moldhttp://en.wikipedia.org/wiki/Moldhttp://en.wikipedia.org/wiki/Water_activity#cite_note-Marianski7-3http://swiftcraftymonkey.blogspot.com/2010/03/fun-with-chemistry-solubility.htmlhttp://swiftcraftymonkey.blogspot.com/2010/03/fun-with-chemistry-solubility.htmlhttp://swiftcraftymonkey.blogspot.com/2010/03/fun-with-chemistry-solubility.htmlhttp://swiftcraftymonkey.blogspot.com/2010/10/question-why-are-we-using-preservatives.htmlhttp://swiftcraftymonkey.blogspot.com/2010/10/question-why-are-we-using-preservatives.htmlhttp://swiftcraftymonkey.blogspot.com/2010/10/question-why-are-we-using-preservatives.htmlhttp://swiftcraftymonkey.blogspot.com/2010/03/fun-with-chemistry-solubility.htmlhttp://en.wikipedia.org/wiki/Water_activity#cite_note-Marianski7-3http://en.wikipedia.org/wiki/Moldhttp://en.wikipedia.org/wiki/Water_activity#cite_note-Marianski7-3http://en.wikipedia.org/wiki/Staphylococcus_aureushttp://en.wikipedia.org/wiki/Bacillus_subtilishttp://en.wikipedia.org/wiki/Listeria_monocytogeneshttp://en.wikipedia.org/wiki/Bacillus_cereushttp://en.wikipedia.org/wiki/Vibrio_choleraehttp://en.wikipedia.org/wiki/Salmonellahttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Clostridium_perfringenshttp://en.wikipedia.org/wiki/Pseudomonas_fluorescenshttp://en.wikipedia.org/wiki/Clostridium_botulinumhttp://en.wikipedia.org/wiki/Clostridium_botulinumhttp://en.wikipedia.org/wiki/Fruithttp://en.wikipedia.org/wiki/Water_activity#cite_note-Marianski5-2


16/23

and bring them back to life. Add a little unbound water to the mix (let's say you have wet

hands and leave a puddle in the top of the product), and you've got yourself a fungal party!

Disclaimer two: How do we figure out how much water is bound in our products and howmuch isn't? There's a lengthy formula that takes into account the water in the product, the

partial pressure of the water vapour above the surface of the product, the relative humidity,and temperature, and by figuring all of that out, we can figure out the water activity of theproduct at that moment.

If I take a look my sugar scrubs, I use about 140% sugar to 100% oils, which means I'mwell above the numbers for killing bacteria and yeast. So should I use a preservative in my

salt or sugar scrub? I'm still firmly on the side of "yes", because I'm always worried about

what the end user will do with the product, but there is some evidence here that you could

use lower levels of preservatives or possibly none. (Please do not take this that I am

endorsing not using preservatives in scrubs!)

Thanks for the question, research, and work you put into your comment, p! It's definitely

food for thought!


17/23

Sucrose. Sucrose has the greatest solubility of the disaccharid sugars. Browne in his"Handbook of Sugar Analysis" states that, at 20C, 204 grams are soluble in 100 cc. of

water. Thus at room temperature about 2 grams of sucrose are soluble in 1 cc. of water. At

100C 487 grams of sucrose are soluble in 100 cc. of water. For solubilities at othertemperatures see Table 5.

In Table 5 the solubility of sucrose is expressed in two ways. In column 2 is given the

amount of sucrose dissolved in water to make 100 grams ofsolution. Thus at 0C, 64.18

grams of sucrose are dissolved in 35.82 grams of water to give a total of 100 grams of

solution. The third column states the number of grams of sucrose dissolved in 100 grams ofwater at a definite temperature.

Table 5 Solubility of Sucrose in Water at Different Temperatures

Temperature,degrees C.

Grams of sucrose in 100

grams of solution, orper

cent

Grams of sucrose

dissolved by 100 grams of

water

Specific gravityof solution

0 64.18 179.2 1.31490

5 64.87 184.7 1.31920

10 65.58 190.5 1.32353

15 66.30 197.0 1.32804

20 67.09 203.9 1.33272

25 67.89 211.4 1.33768

30 68.70 219.5 1.34273

35 69.55 228.4 1.34805

40 70.42 238.1 1.35353

45 71.32 248.7 1.35923

50 72.25 260.4 1.36515

55 73.20 273.1 1.37124

60 74.18 287.3 1.37755

65 75.18 302.9 1.38404

70 76.22 320.5 1.39083

75 77.27 339.9 1.39772

80 78.36 362.1 1.40493

85 79.46 386.8 1.41225

90 80.61 415.7 1.41996

95 81.77 448.6 1.42778

100 82.87 487.2 1.43594
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18/23

Percentage of Sucrose in Saturated Solutions. From Table 5 the percentage of sugar may beobtained. At 0C, 64.18 grams of sugar and 35.82 grams of water give 100 grams of

solution, so that the number of grams of sugar may be read as percentage of sucrose or

64.18 per cent.

Solubilityis a direct function of temperature. As temperature increases, solubility also increases

and vice versa. Therefore, more sugar would dissolve in hot water than in cold water. That means

that the saturation point in hotter water is higher than that in cooler water.

When the temperature is decreased, the solubility of sugar in water decreases. But the water

contains more sugar than this solubility because it was dissolved at a higher temperature. So, what

happens here is that the amount of sugar above the saturation limit at this cooler temperature

comes out of the solution.

We see this as formation of sugar crystals in the water.

Temperature and Solubility of Solids

Increased temperature usually increases the solubility of solids in liquids. To understand why, we

need to return to the Second Law of Thermodynamics. Increased temperature means a greater

average velocity for the particles. This allows them to move from one position to another more

easily. The greater freedom of movement allows the system to change its state more easily, and in

keeping with the Second Law, it changes to the most probable state available, that is, the most

dispersed state of which it is capable. Solids are very condensed systems, so the dissolving of a

solid usually leads to a more dispersed system. Therefore, although there are exceptions, an

increase in temperature generally leads to an increase in a solids solubility. The table below shows

the change in solubility with changing temperature for glucose in water.

Solubility of Glucose

TemperatureSolubility in grams of glucose per 100 mL of

water

25 C 91

30 C 125

50 C 244

70 C 357

90 C 556

The change in solubility with change in temperature can be used to create solutions with more

solute dissolved than is predicted by the solubility of the substance. For example, the solubility of

glucose at 25 C is 91 g glucose per 100 mL of water, and the solubility of glucose at 50 C is 244 g

glucose per 100 mL of water. Therefore, if we add 100 g of glucose to 100 mL water at 25 C, 91 g

dissolve. Nine grams of solid remain on the bottom, and the solution is saturated at this

temperature. If we then heat the mixture to 50 C, the remaining 9 grams of glucose will dissolve.
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19/23

At the new temperature, the solubility limit in 100 mL of water is 244 g glucose. With only 100 g of

glucose dissolved, our system is now unsaturated.

If we now slowly cool the mixture back to 25 C, 9 g of glucose should precipitate from solution.

Sometimes this happens immediately, but sometimes it takes a while for the glucose molecules to

find their positions in a solid structure. In the time between the cooling of the solution and the

formation of glucose crystals, the system has a higher amount of dissolved glucose (100 grams)

than is predicted by the solubility limit at 25 C (91 grams). Because the solution contains more

dissolved solute than is predicted by the solubility limit, we say the solution is supersaturated.

Rock candy is produced from a supersaturated solution of sugar. You can make it by adding more

sugar to water than will dissolve at room temperature, heating the mixture until the solubility limit

has been increased enough to allow all of the sugar to dissolve, suspending a string in the hot

solution, and allowing the solution to cool slowly back to room temperature. The solution remainssupersaturated for a long while. Sugar molecules, which are relatively large, are slow to find the

proper positions for crystal formation. Meanwhile, collisions with water molecules keep knocking

them apart. Eventually, however, solid begins to form on the protected, irregular surfaces of the

suspended string. Dissolved sugarmolecules collide with the solid precipitating onto the string andgradually create the large, well-formed sugar crystals that we call rock candy.

Total Maximum Solubility With Cane Sugar And Invert Sugar


20/23

(Tarr and Baker)

Temperature,

C.

Grams of canesugarper

100 gramssolution

Grams of invert sugar per

100 grams solution

Grams of water per 100

grams solution

20 37.1 38.6 24.3

25 35.7 41.4 22.9

30 33.4 45.6 21.0

Tolman, Munson, and Bigelow in 1901 obtainedresults, which we are now able to interpret on the

basis of our present knowledge, on the inversion of sucrose by juices of differentfruits. Their work

was published before hydrogen-ion concentration was thought of in connection withjellymaking.

After determining the amount of invert sugar in a series of jellies and jams that they had made,

they concluded that the inversion of the sucrose varies with the total amount of free organic acid

present and the length of time the product is heated. But they found some exceptions to their

conclusions. Crab-apple jelly with 0.17per centacid (as sulfuric) gave an inversion of 58.8 per cent

of the sucrose, whereas orange jelly of the same acidity gave only 4.9 per cent of sucrose inverted.Since the inversion is in proportion to the hydrogen-ion concentration if time of heating is

constant, the greatest inversion occurred with the acid giving the highest hydrogen-ion

concentration, the tartaric acid of the grape. In this instance the total acidity was higher too. Plum

with a high total acidity of 1.35 per cent yielded a lower percentage inverted than the grape with a

total acidity of 0.69 per cent. The plum contains malic acid, which would result in a lower

hydrogen-ion concentration than the tartaric.

Why Do Some Soli ds Di ssolve in Water?

The sugar we use to sweeten coffee or tea is a molecular solid, in which the individual

molecules are held together by relatively weak intermolecular forces. When sugar dissolves

in water, the weak bonds between the individual sucrose molecules are broken, and these

C12H22O11 molecules are released into solution.

It takes energy to break the bonds between the C12H22O11 molecules in sucrose. It also takes

energy to break the hydrogen bonds in water that must be disrupted to insert one of thesesucrose molecules into solution. Sugar dissolves in water because energy is given off when

the slightly polar sucrose molecules form intermolecular bonds with the polar water

molecules. The weak bonds that form between the solute and the solvent compensate forthe energy needed to disrupt the structure of both the pure solute and the solvent. In the
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case of sugar and water, this process works so well that up to 1800 grams of sucrose can

dissolve in a liter of water.

Ionic solids (or salts) contain positive and negative ions, which are held together by the

strong force of attraction between particles with opposite charges. When one of these solids

dissolves in water, the ions that form the solid are released into solution, where theybecome associated with the polar solvent molecules.

H2O

NaCl(s) Na+(aq) + Cl

-(aq)

We can generally assume that salts dissociate into their ions when they dissolve in water.Ionic compounds dissolve in water if the energy given off when the ions interact with water

molecules compensates for the energy needed to break the ionic bonds in the solid and the

energy required to separate the water molecules so that the ions can be inserted into

solution.

Solubility Equili bria

Discussions of solubility equilibria are based on the following assumption: When solids

dissolve in water, they dissociate to give the elementary particles from which they are

formed. Thus, molecular solids dissociate to give individual molecules

H2O

C12H22O11(s) C12H22O11(aq)

and ionic solids dissociate to give solutions of the positive and negative ions they contain.

H2O

NaCl(s) Na (aq) + Cl-(aq)
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When the salt is first added, it dissolves and dissociates rapidly. The conductivity of thesolution therefore increases rapidly at first.

dissolve

NaCl(s) Na+(aq) + Cl

-(aq)

dissociate

The concentrations of these ions soon become large enough that the reverse reaction startsto compete with the forward reaction, which leads to a decrease in the rate at which Na

+

and Cl-ions enter the solution.

associate

Na+(aq) + Cl

-(aq) NaCl(s)

precipitate

Eventually, the Na+

and Cl-ion concentrations become large enough that the rate at which

precipitation occurs exactly balances the rate at which NaCl dissolves. Once that happens,

there is no change in the concentration of these ions with time and the reaction is atequilibrium. When this system reaches equilibrium it is called a saturated solution,because it contains the maximum concentration of ions that can exist in equilibrium with

the solid salt. The amount of salt that must be added to a given volume of solvent to form a

saturated solution is called the solubility of the salt.

Solubil ity Rules

There are a number of patterns in the data obtained from measuring the solubility of

different salts. These patterns form the basis for the rules outlined in the table below, whichcan guide predictions of whether a given salt will dissolve in water. These rules are based

on the following definitions of the termssoluble, insoluble, andslightly soluble.
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A salt is soluble if it dissolves in water to give a solution with a concentration of at

least 0.1 moles per liter at room temperature.

A salt is insoluble if the concentration of an aqueous solution is less than 0.001 M at

room temperature.

Slightly soluble salts give solutions that fall between these extremes.

Solubility Rules for Ionic Compounds in Water

Solubl e Salts

1. The Na+, K

+, and NH4

+ions formsoluble salts. Thus, NaCl, KNO3, (NH4)2SO4,

Na2S, and (NH4)2CO3 are soluble.

2. The nitrate (NO3-) ion formssoluble salts. Thus, Cu(NO3)2 and Fe(NO3)3 are

soluble.

3. The chloride (Cl-

), bromide (Br-

), and iodide (I-

) ions generally formsolublesalts. Exceptions to this rule include salts of the Pb

2+, Hg2

2+, Ag

+, and Cu

+ions.

ZnCl2 is soluble, but CuBr is not.

4. The sulfate (SO4-) ion generally formssoluble salts. Exceptions include

BaSO4, SrSO4, and PbSO4, which are insoluble, and Ag2SO4, CaSO4, and Hg2SO4,

which are slightly soluble.

I nsoluble Salts

1. Sulfides (S-) are usually insoluble. Exceptions include Na2S, K2S, (NH4)2S,

MgS, CaS, SrS, and BaS.

2. Oxides (O-) are usually insoluble. Exceptions include Na2O, K2O, SrO, and

BaO, which are soluble, and CaO, which is slightly soluble.

3. Hydroxides (OH-) are usually insoluble. Exceptions include NaOH, KOH,

Sr(OH)2, and Ba(OH)2, which are soluble, and Ca(OH)2, which is slightly soluble.

4. Chromates (CrO4-) are usually insoluble. Exceptions include Na2CrO4,

K2CrO4, (NH4)2CrO4, and MgCrO4.

5. Phosphates (PO4-) and carbonates (CO3

-) are usually insoluble. Exceptions

include salts of the Na+, K

+, and NH4

+ions.

recipes for growing sugar crystals

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