New standards for acid etching and sand blasting: what glass processors need to know

New standards for acid etching and sand blasting: what glass processors need to know

Featured Article
06 Feb 2019

As Featured in GGP Magazine - 08/18

Phil Brown, European regulatory marketing manager at Pilkington United Kingdom Limited, part of the NSG Group, discusses how new harmonised standards for acid-etched and sand-blasted glass will help glass processors to secure CE marking for products and deliver uniformity to the industry.

Acid etching and sand blasting are processes often used to create decorative, translucent glass that can help to create privacy in buildings. Despite this, it has never been possible for these products to be CE marked, the main way in which a construction product can legally be sold in the EU.

The reason for this odd situation is that there are currently no harmonised European standards to cover them.

However, this is set to change with the development of two new European Standards due to arrive in 2019. Glass manufacturers will need to understand the requirements of these in terms of testing products and production processes and, ultimately, this should provide a formal and consistent basis for comparing these products across the industry.

The two new draft standards for acid-etched glass (prEN 17257) and sand-blasted glass (prEN 17258) are split into two parts – definitions & descriptions, and product standard. So, what are the key details of each that processors need to be aware of?

Acid etched glass: definitions and scope

Acid etched glass is simply defined in Part 1 as a glass product where one or more of its surfaces has been etched with either acid, its compounds, or its salts, to give it a translucent appearance.

The scope of prEN 17257 is acid etching done on various types of glass, including heat treated glass, where the surface finish is applied as the final process. But, it does not apply to glass where further processing, like toughening, has taken place following the surface finish being applied. 

Part 1 specifies tolerances and requirements for the visual appearance of the product. The processor will need to assess how the glass looks and check for uniformity as well as any defects. Depending on the specific application, the standard considers other properties of acid-etched glass such as slip resistance, privacy, anti-reflection and decoration.

Sand-blasted glass: definitions and scope

Sand-blasted glass is defined by the new standard as a glass product where one or more surfaces has been blasted with a fine abrasive to give it a translucent appearance.

It covers the process in respect to various types of annealed glass, where the surface finish is applied as the final process. As with the new acid etching standard, it doesn’t apply to glass where further process (e.g. toughening) has taken place after the surface finish has been applied. 

Part 1 specifies tolerances and requirements for visual appearance, where the processor is again required to assess uniformity and defects. Other properties are considered dependent on applications like slip resistance, privacy and decoration.

Cleaning, processing and installation

Both standards also provide guidance on cleaning, processing and installation. The advice includes ensuring that sealants or adhesives do not adversely affect the appearance. Plus, the standards recognise how, in bathrooms for example, translucency may be reduced as the glass becomes wet.

When fabricating the glass into an insulating glass unit (IGU), the standards recommend that the surface finish should be inward-facing where possible, eliminating any risk of marking, although the IGU manufacturer should still ensure that there is an appropriate level of adhesion between the sealant and surface finish.

What happens next?

Companies carrying out acid etching or sand blasting will need to start preparing for CE Marking.  A product description will also need to be generated covering relevant standards and the range of surface modifications applied and glass substrates used. If not already in place, a Factory Production Control system will need to be set up to check incoming materials, process control and post-processing inspection. Samples will have to be produced for type testing, including measurement of light and solar properties. 

The draft standards have been out for consultation and responses will now be reviewed by the Comité Européen de Normalisation (CEN) technical committee working group responsible for the standard. A revised draft will then be published ahead of a formal vote to deliver the final approved standard.

If and when approved, the harmonised standards will be cited in the Official Journal of the European Union, usually with a 12-month transition period. Gazing into the CEN crystal ball to make predictions is tricky, but we could see CE Marking of acid etched glass and sand blasted glass commence in the second half of 2019. Processers, on your marks!

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