Kilns are very hard working tools. Afterthe first few firings, the steel case of a newkiln discolors and hairline cracks appearin the firebricks. This is normal.

Though the insulating firebrick is frag-ile enough to carve with a fingernail, it is amiracle of physics. It can routinely with-stand temperatures over 2000°F, which ishot enough to melt copper, bronze, brass,and aluminum. Nevertheless when prop-erly maintained, firebricks can survivemany hundreds of firings.

The high temperatures inside a kiln cause tremen-dous stresses. Since the insulating firebricks expand andcontract with each firing, cracks appear in the brickswhile the kiln is cold. Do not be concerned with these.The cracks close tightly when the heated bricks expandand function as expansion joints.

Cracks in the firebrick bottom usually should not berepaired. As long as you are supporting the kiln with thecorrect stand and the kiln case is tight, the cracks in thebottom are nothing to worry about.

If you use silica sand on the kiln shelves, be careful notto allow the sand to seep onto the firebrick bottom. Thesand will get into the cracks and widen them.

Do not be concerned with the line of light that appearsaround the edge of the door or lid at high temperatures.This is due to the natural expansion of the firebricks anddoes not affect the firing.

It is okay to open the kiln lid or top a half inch or so for afew seconds to check on the hot glass inside. This has lit-tle effect on the life of the firebricks.

PreventiveMaintenance

Caution: Do not breathe the dust that formswhen you vacuum the kiln or mix kiln wash. Weara mask.

Vacuum the KilnOne of the easiest kiln maintenance tasks you can per-

form is regular vacuuming. This is especially important ifyou fire glazes. Vacuum the kiln before every glaze firing.

Use the soft brush nozzle on a vacuum cleaner. Besure to vacuum the element grooves, the inner surface ofthe kiln lid or roof, and the underside of kiln shelves.

Vacuuming the grooves is essential if clay has explodedinside the kiln. Pieces of greenware that lodge inside thegrooves can cause element failure.

Vacuum the kiln often if you use silica sand on theshelves to support ware. Sand can ruin the elements if itfilters down into an element groove.

As you vacuum the kiln, examine the walls for glass orglaze particles that have embedded into the firebricks.Dig these out carefully with a screwdriver.Coat the Brick floor

Coat the firebrick floor of your kiln with kiln wash orglass separator. Do this even if you are firing only glassand feel that you will never overfire your kiln. (The kilnwash or glass separator must be rated to 2400°F.)

Pour water into a disposable container and addpowdered kiln wash until it has the consistency ofcoffee cream. Stir until lumps dissolve.

Apply three thin layers of kiln wash rather than onethick layer. You can use a small paintbrush or aChinese haik brush. Allow the kiln to dry beforefiring.

If the kiln wash cracks or flakes off, reapply it only tothe bare spots. Do not remove the kiln wash from the fire-brick floor and apply a fresh coat. This is unnecessary andmessy.

Avoid splashing kiln wash onto the firebrick walls, es-pecially if you have sidewall elements. Contact with kilnwash and glass separator destroys elements, often duringthe next firing.

Do not apply kiln wash to ceramic fiber firing cham-bers. Kiln wash is meant for firebricks and ceramicshelves.

Note: Leave the floor uncoated if your kiln has anelement in the floor.

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Firebrick Maintenance

©2007, by Paragon Industries, L.P. IM-234/6-07

Coat the firebrick floor with kiln wash or glass separator. If your kilnhas sidewall elements, hold a piece of cardboard in front of the ele-ments to protect them from contact with kiln wash.

Fire Dry Ware and ShelvesGreenware and shelves should be bone-dry and warm

to the touch. If you must fire moist ware, wait until allsigns of vapor have disappeared before heating past 200°F. At higher temperatures the moisture turns to steam,which is not good for the firebricks and can cause theware to explode.Top-Loading Kilns: Extending Life ofTop Wall Bricks

The wall area of a top-loading kiln that is most prone tobrick damage is the top rim of sidewall firebricks. This isbecause people lean against the edge of the kiln to loadand unload. Place as little weight as possible on the kiln.

Reduce brick damage by cutting a piece of plywoodabout 3” - 4” wide shaped to fit over the edge of the kilnwhen the lid is open. Lean against the plywood instead ofdirectly against the brick rim. The plywood should becurved to the shape of the kiln. The plywood will help dis-tribute weight evenly against several bricks instead of onlyone.Be Gentle with the Kiln

During loading and unloading, do not touch the side-walls of the kiln with anything. Do not allow a shelf tobump into the firebricks. The extra time and care youspend loading and unloading may add years of life to yourkiln.

Allow only trusted people to load and unload your kiln.They must be gentle, or your kiln will quickly show wear.Do not let your students touch your school kiln until youhave given them a lesson in care of the kiln.

Lower the kiln lid (or close the kiln door) gently. Slam-ming the lid can crackthe bricks the firsttime it happens.

Lids with a lockingsupport arm: Fullydisengage the arm be-fore lowering the lid.Otherwise you canbreak the lid near thehinge. Lids with aspring counterbalance: Hold the lid handle and guide thelid until it is fully opened. If you let go of the handle toosoon, the lid will slam back, damaging the bricks.

From time to time, check the condition of the lid sup-port or spring system and the lid handle.

Keep the lid closed when you are not using the kiln.This keeps dust out and prevents the lid from droppingwhile you are away. Do not store anything inside the kilnor on top.

When firing heavy loads in the kiln, place a spare shelfdirectly onto the kiln floor. The shelf spreads the weightof the load over the entire floor.

Most large kilns are designed to be fired on a kilnstand. It raises the kiln off the floor and helps to dissipateheat under the kiln. The top of the stand should be di-rectly under the kiln walls. A stand that is too small for thekiln will strain the brick bottom.

The kiln stand should be level and rock-steady. Anunlevel stand can stress the firebricks. A stand that rockscan cause the kiln to move when jarred, knocking overware against the sidewalls inside the kiln.

Remove Melted Glaze and Glass from the BricksIf glaze, glass, or other materials drip onto a kiln wall or

the kiln floor, repair before the next firing. Otherwisethese materials will remelt and embed deeper into thefirebricks. Remove the contaminant by scraping gentlywith a putty knife. If you remove kiln wash from the kilnfloor, apply a fresh coat to the bare spot.

Repair CementTechniques

The purpose of the firebricks:1) Insulate the firing chamber2) Support the heating elementsDo not repair damaged bricks as long as they continue

to insulate the kiln and to support elements. (An excep-tion: Dust is falling from the brick roof.) Most firebrickdamage is cosmetic and does not affect the firing results.Examples of cosmetic damage:

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Be gentle. Slamming the lid can break thefirebricks.

Minor lid damage. Since it is on the edge, dust will not fall into the firingchamber. To repair, sand lightly and coat (see next page). But do not fill.

This is minor damage. It should not be repaired because the element doesnot bulge outside the groove; the brick still supports the element. Also, thegroove does not insulate the kiln. The part of the firebrick that insulates isbetween the kiln’s outer steel case and the elements.

Some of the reasons to repair firebricks:� The lid coating is flaking onto the ware.� Dust is falling onto the ware from lid cracks.� An element pin in the lid is falling out.� Glaze or glass has embedded into a wall or floor.

� An element is sagging because of a damaged brickgroove.

� You need to plug a vent hole.

Coating the Kiln LidOn top-loading firebrick kilns, the inside of the lid and

top rim of wall bricks can be coated for longer wear. Liq-uid Kiln Coating is a refractory cement that we have for-mulated for coating firebrick lids here at the factory. (Thedoor or lid of ceramic fiber kilns and front-loading fire-brick kilns do not need the coating.)

The coating hardens and protects the firebrick sur-faces. One application lasts through many firings eventhough the coating will seem to disappear after the firstfiring.

If you splash the coating onto an element, remove asmuch of the cement as possible from the element. Do notfire the kiln until the coating is completely dry.

Coating that is applied too thick will flake off the lid af-ter you fire the kiln. If the roof or inner surface of the lid

peels, sand the peeled area of the lid and apply kiln coat-ing to the bare spots.

If you are coating over a freshly patched firebrick sur-face, allow the cemented patch to dry first.Liquid Kiln Coating Instructions

Shake the container until the liquid coating is thor-oughly mixed. Pour some of the coating into abowl. Stir the coating just before you apply it to thefirebricks.

Apply the coating with a large, soft sponge such asthe type used for wallpaper. Moisten the spongewith water squeezing out the excess.

Dip the moistened sponge into the bowl of kilncoating. Wipe the coating over the lid surface.Work quickly, and wipe off the excess. The coatingshould be thin enough so that you can still see thegrains of the bricks underneath.

Allow the coating to dry completely before firingthe kiln.

Repair Cement BasicsWe use Paragon’s Liquid Kiln Coating & Repair Ce-

ment at the factory to make lids and bottoms. It comes inpint bottles.

The thinner the cement seam, the better. Try tomake the two firebrick surfaces match as closely aspossible for a thin seam.

Vacuum all firebrick surfaces that are to be ce-mented. Remove all traces of dust. (If you do nothave a vacuum, you can remove dust with a drypaintbrush or with canned air. Do not breathe thebrick dust.)

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Sand the peeled areas of the lidand reapply the coating.

These cracks in the brick floor close tightly during firing.

A damaged top brick in a top-loading kiln does not need to be repaired solong as 1 ½” of brick surface remains to form a seal against the lid. Thebrick still supports the element.

Spray a fine mist of water onto both firebrick sur-faces before cementing. Mix 1 drop of liquiddishwashing soap to 1 cup of water. The soap re-duces surface tension of the water to help it ab-sorb into the bricks. Use a small spray bottle.

Note: Water is unnecessary if you work rapidly.The water on the bricks merely allows you moretime to work with the cement.

After you have cemented the firebrick pieces andpressed them tightly into position, do not reposi-tion the pieces. Otherwise the bond may nothold. If you move the pieces after the cement hasset, you will see hairline cracks in the cement. Inthis case, remove the repair piece and cementand start over from the beginning.

Gently wipe off excess cement from the bricksurface. However, do not sand smooth until thecement dries overnight.

Speed-Drying the CementSometimes it is necessary

to dry the cement quickly sothe patched firebrick piecedoesn't fall out of place. Thistechnique allows you to patchdifficult areas such as a lid orroof. Speed-drying the ce-ment eliminates the need tohold a prop against the re-paired lid while the piecedries.

After you have cementedthe brick patch, heat the ce-ment seam with a propanetorch. Hold the torch 5 - 6 inches away from the firebricksurface for about 10 seconds.

(Otherwise you may heat-shock the wet ce-ment.) Let the patch dry overnight before firing the kiln.

You can purchase a propane torch from a home im-provement center. Buy the type that has a push-buttonigniter. When you press the button, a blue flame appears.When you release the button, the flame goes out.

For kiln maintenance, do not use the older manualpropane torches. Turning them on and off is awkward.You first turn a knob to start the flow of propane and thenhold a match under the nozzle. The push-button type ismuch safer and worth the extra expense.

Powdered Firebrick FillerDo not fill in firebrick gouges or low spots with solid

repair cement. When applied as a filler, the cement willbreak out later from the firebrick due to a difference inthermal expansion between the cement and the brick.

Fill brick gouges with Kaolin Grog mixed with repaircement. (Kaolin Grog, available in 5 lb. bags, is powdered

firebrick.) Kaolin Grog fillermore closely matches the coeffi-cient of expansion of the fire-brick and stays in place. Add justenough cement to hold the Ka-olin Grog together.

Note: The gouged firebrickfloor shown in the photos atright does not need to be re-paired. We simply used thisas an example. Smallgouges in the brick floor donot affect firing results.

Making Firebrick PatchesPatching a broken firebrick is not difficult. It just re-

quires patience and a little practice. Make firebrickpatches to repair the lid, walls, and floor of a kiln.Firebrick Sanding Blocks

Use coarsesandpaper suchas 285 grit tomake a sandingblock. Removethe peel-awaybacking froms e l f - a d h e s i v esandpaper andstick the sandpa-per to the sandingblock.

For sandingsmall firebricksections, you mayneed a sandingblock as small as½” x 1”. Bandingsteel, which isused to reinforceshipping crates,makes a goodminiature sand-ing block. Bend a6” piece of banding steel 90 degrees at one end. Thelength of the bend should be whatever size block youneed, such as 1". Then cut the sandpaper to the correctsize, peel off the sandpaper backing, and press the sand-paper onto the outer bent end of the banding steel.

You can also make sanding blocks from strips of sheetmetal, wood, etc.Repairing The Damaged Brick

Practice patching firebrick scraps before working onyour kiln.

With a hacksaw blade, cut an outline around thebroken brick section. Cut a small rectangle orsquare.

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Sanding blocks made with 285 grit self-adhe-sive sandpaper. The block on the right is madefrom banding steel.

The left sanding block is 1 ¼” wide; the rightsanding block is 1” wide. In the center is a hack-saw blade used to cut firebricks.

Use the hacksaw or small sanding block to removemost of the brick within that outline. Then sandthe brick to smoothen the bottom of the recess. Ifthe repair section is small, you will need a minia-ture sanding block.

After the recess is smooth, make a firebrick pieceto fit into the recess. The piece should be a littlesmaller in width and depth so that the brick seamis 1/16” or less on all sides. Spend time to make theplug fit precisely. The seam should be only 1/16”.A thicker seam may break later due to the differ-ence in expansion between the firebrick and ce-ment.

Use a brush, vacuum cleaner, or canned air to re-move the dust. (Wear safety glasses when usingcanned air.)

Spray a fine mist of water onto all mating brick sur-faces.

Working rapidly before the water dries out, wipefirebrick repair cement onto mating surfaces.

Press the plug tightly into place. Do not move itonce the mating surfaces make contact. Hold thebrick piece for one minute.

Remove excess cement while it is still wet. Allow todry for 24 hours. Then sand the surface smooth ifnecessary.

Plugging a FirebrickHole

You can make a fire-brick insert to fill a drilledfirebrick hole:

Cut a firebrick that isthe same length as thewidth of the kiln walland slightly larger thanthe hole you are filling.

With a sanding block,round the firebrickpiece. It should be1/16” smaller in diam-eter than the hole.

Coat the plug with re-pair cement and insertinto the hole until the plug is flush. Wipe off excesscement. If necessary, sand after the cement hasdried.

Cementing Broken PiecesBroken firebrick pieces can be cemented together

provided there is enough surface area for the bond.Use a brush, vacuum cleaner, or canned air to re-move the dust. (Wear safety glasses when usingcanned air.)

Spray a fine mist of water onto all mating brick sur-faces. Mix 1 drop of liquid dishwashing soap to 1cup of water. The soap reduces surface tension ofthe water to help itabsorb into thebricks.

Working rapidly be-fore the water driesout, wipe firebrickrepair cement ontomating surfaces.

Press the piecetightly into place.Do not move it oncethe mating surfacesmake tight contact.Hold the brickpiece for 1 minute.

Allow to dry for 24hours. Then sandsmooth if necessary.

Cementing Flat SectionsWhen cementing firebricks together, make the ce-

ment seam as thin as possible—1/32" - 1/16". If the seamis too thick, it will break due to the difference in expansionbetween the bricks and the cement.

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Use this technique to repair walldamage where the lid touches thekiln wall.

The ideal way to cement bricks together is along flatsurfaces, because sliding the surfaces together after ap-plying the cement makes a thin seam.

First, the bricks you are cementing should fit asprecisely as possible. Rub the surfaces with asanding block, and then rub them against eachother until they slide smoothly. Vacuum all sur-faces.

Pour the cement into a 12" x 36" galvanized steelor plastic tray.

Do not spray or soak the mating brick surfaces inwater. That is unnecessary, because by dippinginto a tray, you can coat the entire brick surfacewith cement in several seconds leaving plenty oftime to work with the cement. Of the two sur-faces you are cementing,dip only one surface intothe cement tray. Leave themating surface dry of ce-ment.

After dipping the bricksinto the tray, do not wipeoff excess cement. Also,do not be concerned withtrying to cover the entirebrick surface with ce-ment. The cement maycling to theouter edgesand not to theinner sectionof the surfacethat you haved i p p e d .That's okay.

Slide the mat-ing surfacestogether. If the ce-ment is mixed with theproper proportion ofwater, the brick sur-faces will slide to-gether smoothly. Toachieve a 1/16" - 3/32"seam, slide the sur-faces back and forth about 5 times, sliding about3" before changing the direction. Each time youchange directions, the seam will become thinner.In a few seconds, it will be difficult to slidesmoothly. The cement has set. Stop moving thepieces.

Allow the cement to dry. After 24 hours you canlift the brick sections without breakage.

Wall RepairsRepairing Firebricks withElement Staples

In some cases, elementstaples (also called pins) canhold small broken bricksections together:

Bend a “U” shapedelement staple withpliers to form an “L”shape.

Fit the broken brickpiece back into the wall where it fell out.

Grasp ane l e m e n tstaple withpliers, andpress thestaple at anangle intothe brokenb r i c kpiece. Usetwo staples tilted away from each other. (Press-ing the staples in at an angle holds the broken

brick better than pressing the staples straightin.) Press the staples until flush with the surfaceof the firebrick. Be careful to avoid pressing a sta-ple into an element. The staple should also beshort enough so that it does not touch the kilncase on the other side of the brick wall.

Alternately, youcan pin elementsin place where abrick groove hasbroken off. Thiswill prevent ele-ments from touch-ing. Press the ele-ment pin over onlyone element coil.

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Replacing Top Firebricks Ona Top-Loading KilnSwitch-Operated Models and Non-Sectional Digi-tal Models:

Raise the lid. Unhook the bottom of the LiteLidspring. Gently lower the lid.

Remove the screws on theLiteLid hinge section that isattached to the back of thekiln. Models without lidspring: Remove the lowerhinge from the back of thekiln.

Gently lift the lid andLiteLid assembly from thekiln.

Remove the top screws thatfasten the stainless steelcase together in the back ofthe kiln. Loosen the bottomscrew, but do not remove it.

Blank 2" high bricks: Lift outthe damaged bricks.Grooved bricks:Heat the element inthe damaged brickswith a propane torchuntil the element isred. Use nee-dle-nose pliers topull the red-hot ele-ment out of the way.Lift out the bricks.

Insert replacementbricks. It may benecessary to sandthe ends for a goodfit. Grooved bricks:Heat the elementthat is to go into thenew bricks with a propane torch until the elementis red. Use needle-nose pliers to push the red-hotelement into the brick grooves.

Line up the screw holes of the case with a kiln casetightener (available from Paragon). Reinstall thescrews that you removed in step 4.

Note: Do notover-tighten screwsespecially if you use apower drill. Set thepower drill on slowspeed.

Reinstall the LiteLid assembly onto the back of thekiln. Attach the bottom of the spring to theLiteLid. Models without lid spring: Reinstall thescrews in the lower hinge.

Sectional Digital Models:

Note: See photos, previous section, and “Separat-ing the Sectional Paragon Kiln,” publicationIM-209.

Raise the lid. Unhook the bottom of the LiteLidspring. Gently lower the lid.

Lift the lid from the kiln.Loosen the screws inthe clamps that hold thetop section of stainlesssteel case together.They are on the side ofthe kiln.

Blank 2" high bricks:Lift out the damagedbricks. Grooved bricks: Heat the element in thedamaged bricks with a propane torch until the ele-ment is red. Use needle-nose pliers to pull thered-hot element out of the way. Lift out the bricks.

Insert replacement bricks. It may be necessary tosand the ends for a good fit. Grooved bricks: Heatthe element that is to go into the new bricks with apropane torch until the element is red. Use nee-dle-nose pliers to push the red-hot element intothe brick grooves.

Insert replacement bricks. It may be necessary tosand the ends for a good fit.

Note: Do not over-tighten screws especially if youuse a power drill. Set the power drill on slowspeed.

Tighten the screws of the case clamps that youloosened in step 2.

Lid RepairsRepairing Lid Cracks

Dust may fall from cracks in the lid. This does not af-fect ceramic greenware, but dust can ruin glazed wareand glass. Before a glaze or glass firing, vacuum the lidcracks. If dust continues to fall even after vacuuming, loadthe kiln so that ware on the top shelf is away from the lidcracks.

You can also stuff the cracks with ceramic fiber. Thecracks must be at least 1/16” wide. Hairline cracks are toosmall to accept the ceramic fiber.

Roll the ceramic fiber in the hands to form a pen-cil-like strand.

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Press it into thecracks with a smallstick or putty knifebeing careful not todamage the fire-bricks further.

Sometimes tighteninga loose lid band helps tokeep cracks from openingwider:

Grasp the clamp with pliers to prevent it fromtwisting.

Tighten thescrew to takeup the slack inthe lid band.Tighten untilthe screwfeels snug.Try not toover tighten.

Replacing the Lid/RoofElement Pins of a Glass Kiln

The elements in the lid or roof of most Paragon glasskilns do not need pins. The element coils are wider thanthe groove opening, so the elements stay in place withoutpins.

The earlier lid/roof elements were held in place withpins. You can use either kiln repair cement or Pyrolite tosecure a pin that becomes loose or falls out. (Pyrolite is arefractory joint adhesive. It comes in a 10.3-ounce plastictube that fits into a caulking gun applicator.)

Unplug the kiln.

Dip the element pin intokiln repair cement orPyrolite. You will needonly a small amount onthe prongs of the pin.

Insert the pin into thefirebrick lid or roof at asharp angle. (If you insertthe pin so that it is verticalwhen the lid is closed, thepin may eventually workits way out of the grooveagain.) Cover only one el-ement coil with the pin.

Caution: Make sure the tipof a pin does not touch an-other pin inside the fire-brick lid or roof.

Optional: Use a screwdriver to gently tap the pinfurther into the lid.

Important: Let the cement or Pyrolite dry com-pletely before firing the kiln.

Securing a Lid/Roof Elementwith Pyrolite

Pyrolite is a refractory joint and patch compound. It co-mes in a 10.3-ounce plastic tube that fits into a caulkinggun applicator.

Note: You can gently move a cold nickel-chromeelement, which is the type that Paragon uses inlid/roof glass kiln grooves. But you should notmove a cold iron-chrome-aluminum element,which becomes brittle after it has been fired. Tofind out which type of element you have, touchthe element with a magnet. Theiron-chrome-aluminum element attracts themagnet; the nickel-chrome element does not.)

Unplug the kiln.

While the element is cold, gently pull the saggingelement section from the groove so that the ele-ment is positioned just out of the groove.

Vacuum the groove. Remove loose debris so thatthe Pyrolite can stick to the firebrick.

Squeeze a bead ofPyrolite into thegroove.

Press the ele-ment into thegroove. It is okayfor the elementto partially em-bed into thePyrolite. But theside of the ele-ment that is to-ward the firingchamber shouldnot be coveredwith Pyrolite.Completely em-bedding the element in Pyrolite could cause theelement overheat.

Allow the Pyrolite to dry completely before firingthe kiln.

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