Vacuum News

Brllmgsgate by Museum of London archaeologists in 1982 It had

been perfectly preserved in the wet, anaerobic silt and consequently

still bears the marks of its construction-tool cuts from saws, axes

and adzes and carpenters’ marks. After being recorded, the quay was

drsmantled and taken to the Museum for conservatron. This was

done by freezed-drying, a process which removed the moisture rn

the wood without causing cracking and warping Polyethylene

glycol, a water-soluble wax, stabilizes the wood.

Thus was the first time that such an rmpressrve prece of medieval

carpentry had been treated In thus way in the UK for display

purposes. It stands as a tribute to the skills of London’s medieval

engineers, present-day archaeologrsts and the hrgh-tech scientrfic

technrques used rn conservatron today

The freeze-drying treatment was carned out by the specralrst firm

Consortrum Conservation of Dundee which came to the rescue with

a 3 m long freeze-dryrng chamber

The freeze-drying process rnvolves freezrng the wood to 20°C and

placing it in a vacuum chamber where the high vacuum causes the

rce in the wood to sublime into water vapour. This is re-frozen rn a

cold trap and removed. Recent experiments have shown that, usrng

polyethylene glycols of a low molecular weight first (to penetrate the

solid heartwood) and then of a high molecular werght (to

consolrdate the spongy surface wood) preserves even the most

difficult timbers.

Further detarls and photographs from: Press and PR Office, Museum

of London, London Wall, London EC2Y 5HN, Tel 01-600 3699 ext

240/280

World’s largest video system front projection mirror made by Kendall Hyde

The world’s largest glass front-surface mrrror measurrng 3 x 1 8 m has

been made by Kendall Hyde for TWS of Preston, a company

specralizrng rn audro visual systems. It forms part of a composite

presentatron unit for the Eastern Electricity Board at Hatfield.

Images from video and slide projectors are drverted onto a rear

projection screen which is large enough to take two rmages srde by

side. This, together with the lack of space behrnd the screen, made It

necessary to use the largest possible mrrror. Normally a smaller mrrror

IS used and the rmage enlarged over a drstance of several feet to

avoid drstortron. Front surface mrrrors are essential in high qualrty

vrdeo applications 11 ghost reflections are to be avorded

Kendall Hyde, the Aldershot based specialist in optical film coatings,

has the largest vacuum chamber in Europe used for optical thin film

coatrngs. Apart from glass front surface mirrors the company can

produce plastrcs mirrors as large as 3000x 2000 mm

The reflecting hrgh purtty (99.99%) aluminrum IS deposrted onto the

surface of the substrate under hrgh vacuum. The film is only fifty

mrllionths of an Inch thick and to protect the surface when in use an

even thinner film of transparent magnesium fluoride IS applied. This

increases durability by givrng the coatrng excellent hardness and

resistance to tarnrshing

This type of coating IS used rn photocopier mirrors, security systems,

astronomrcal mirrors, tv and audio visual equipment, optical

instruments and for discotheque effects

Beamsplitters or two way mrrrors for secunty use are produced rn a

variety of transmrssion/reflectron ratros according to the operating

conditrons.

Kendall Hyde specralizes rn vacuum deposrtron of thrn film

aluminium, gold, silver, chrome, nichrome, inconel and trtanrum

droxrde coatings on various substrates for many applications

requrrrng hrgh optical qualrtres.

Make Kendall, Managrng Drrector

Kendall Hyde Ltd

Unrt 4, Blackwater Way lndustnal Estate, Aldershot. Hants GUI 2 4DL

Tel 0252 313881

Edwards 2001 Controller aids semiconductor production

Durrng the last 24 years Slee Semiconductor Equipment Co Ltd has

achieved a world-wade reputation for this semiconductor

encapsulation equipment which IS considered to be the most

advanced avarlable today.

This equrpment normally comprises a sophrstrcated semrautomatrc

projection welder contarned in an environmentally controlled glove

box suite wrth a vacuum processing oven attached

Production manager Doug Riley, at Slee Semiconductor rn South

London, says: ‘Our capacitron, synchronous and seam welder surtes

can be---and generally always are----supplied with a vacuum oven

controlled by an Edwards 2001 Controller which controls the

nrtrogen vent/vat cycle during processrng

‘Since we vent/vat up to none times It is important to us and our

customers that the controller is both easy to operate and reliable The

2001 provides just that combrnation It is simple to programme and

secunty is easily achreved vra a password that can be easily built-In

Depending upon the gauge heads fitted, the Edwards 2001

Controller has a range of 1 OOO- 5 * 10 * mbar. It is supplred as

standard wrth one Pirani module whrch IS able to drive two gauge

heads and one Penning Module whrch drives one gauge head Two

further gauge modules, erther Piranr or Penning, can be fitted If the

process demands this. Up to 32 input/output channels can be used

to drive the external relay unrts or opto-Input units. The 2001 IS

capable of expansion up to a total of 64 input/output channels.

In addmon to the Edwards 2001 Controller, Slee also use Edwards

pumps of differing sizes depending upon their customer’s

requirement.

While British companres such as GEC, Ferrantr, Marconr and Plessey

have all become significant customers of Slee, therr most dramatrc

growth has come in the USA during the last five years

Edwards Hugh Vacuum

Manor Royal, Crawley, West Sussex RHI 0 2LW

Tel 0293 28844

Physical vapour deposition-equipment and service

D G Teer Coating Services Ltd now has available a wide range of

physical vapour deposition equipment and services. The company

offers consultancy rn all aspects of PVD rncludrng rf or dc rcn

platrng, magnetron sputtering, electron beam gun and arc source

evaporatron. New coatrngs and coating processes are developed by

means of customer sponsored projects. Short term feasrbilrty studies

or ‘trouble-shooting’ exercises are also offered. Equipment avarlable

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