Cumbria Crystal - Acid polishing service for UK glass artists

Cumbria Crystal is one of the last producers of luxury hand-blown and cut 30% lead crystal stemware in the country. All production processes are carried out at the factory in Ulverston, Cumbria including blowing, cutting and acid polishing.

Due to the dangerous nature of acid polishing process and environmental risks, the process is no longer common in the UK so is not readily available. Understanding the challenges faced by glass artists we have decided to explore the offer of an acid polishing service to the art glass world.

Many artists end up polishing by hand or finishing works with semi-permanent sealers. At best these approaches can be time consuming - at worst they look poor, offer a temporary finish, artificially inflate costs, reduce profit margins or even push work into the ‘unaffordable’ bracket. We hope that this service will offer a realistic alternative professional finish.

The hydrofluoric/sulphuric mixture works effectively on lead crystal only, so will be of interest primarily to glass casters working with Gaffer Glass or alternative lead crystal, or blowers using 24% + crystal. It will not work effectively with other glasses.

Information to help ensure a quality finish:

 Sandblast or wash glass to remove all mould residue from cast objects.

 Glass with exposed metal or other inclusions is unlikely to be suitable as they will dissolve.

 The quality of finish depends on the quality of preparation. Scratches will not be removed

– the glass may end up shiny but the scratch will still remain.

o Manually prepare glass to between 320-600 grit equivalent – grinding, cutting, etc. A textured rough surface will respond differently to a semi-polished surface.  Crystal in secured in special baskets suitable for immersion in the acid.

 Crystal will be pre-heated in a hot water tank for a number of hours to minimise the risk of thermal shock when immersed in the acid. Good annealing is therefore essential.

 A typical full polish cycle for our 30% lead crystal is 42 minutes at approx. 52°C. o baskets containing glass are picked up by a mechanical arm and go through a series of acid immersions, with agitation (to try & ensure even polishing), hot water rinses and neutralisation.

 It is possible to immerse crystal for just a few minutes to achieve a satin finish.

 Maximum basket capacity – around 15kg.

 Maximum basket dimensions H30xW30xD40cm o More than one item may be held in a basket depending on size.

CUMBRIA CRYSTAL· UNIT 4 · CANAL HEAD· ULVERSTON · CUMBRIA· LA12 7LB · ENGLAND

T +44 (0)1229 584 400 E MAIL INFO@CUMBRIACRYSTAL.COM

WWW.CUMBRIACRYSTAL.COM

REGISTERED IN ENGLAND NO. 4007451 · GREATDALE LTD TRADING AS CUMBRIA CRYSTAL · REGISTERED ADDRESS, LOWTHER HSE, LOWTHER ST, KENDAL, CUMBRIA LA9 4DX

 Internally colour cased blown vessels should have clear glass applied to the iron prior to adding colour. This will help prevent acid stripping away colour on the inside due to the presence of a layer of clear.

 Vessels with a narrow neck can be water filled, & stoppered to prevent acid entering.

 It is possible for crystal to pick up ‘rack marks’ from the materials on which it is supported in the basket if they impede the movement of acid round the object or prevent the glass moving slightly during the polishing cycle.

 Different lead contents react differently to the acid so results may be a little unpredictable.

Contact Cumbria Crystal for further information about the potential to acid polishing your products. Since glass artists’ products vary so enormously it will be useful to have photographs or drawings available to help us understand exactly what is involved in polishing your products.

Please contact us on info@cumbriacrystal.com or call +44 (0)1229 584 400 to discuss.

Chris Blade MA (RCA)

Managing Director