Glass Terminology

Q What is Float Glass?

Glass produced by the Pilkington-invented Float system - which gives near-perfect, flat, clear glass from 1.25-25+mm in thickness. Float glass has almost completely replaced other forms (see Sheet and Cast/Rolled glass) of flat glass production and is the base product from which virtually all other flat glass products are manufactured. Typically, 2mm float will transmit 90% of visible light, reflect 8% and absorb 2%. UV light filtering is approx. 45%.

Click here to view a diagram of float glass production, including the coating process (where appropriate).

TOP

Q What's the Difference Between Float & Sheet Glass?

Sheet glass is (was) produced by 'drawing' the molten mix through rollers to achieve the desired thickness of panel. This process left roller marks (areas of differing thickness) which caused the once familiar waviness. Sheet production virtually ended when the new float glass process was introduced in the 1970s. Float is produced by floating the molten raw material on a bath of molten tin. As the (continuous) ribbon of glass proceeds (floats) along the tin bath, it is cooled gradually until it has hardened enough to go off into a conveyor system (the tin remains molten at this stage) for cutting and packing.

As float is produced "liquid floating on liquid" it is perfectly flat and has a superb 'polished' surface finish. The float process invented by the British firm Pilkington, is frequently described as the most radical change to an industrial process since the war.

TOP

Q What is Diffused-Reflection Glass?

Also known (in USA particularly) as "non-glare" and, incorrectly, as non-reflecting glass, these are glasses with one or both surfaces altered to scatter or diffuse the reflected portion of visible light. This gives a much wider viewing angle to artwork - particularly under harsh lighting. It does reduce image contrast and clarity --particularly if used over mountcard(s). Two methods of surface alteration are used:

i. Acid-etching
ii. Casting/Rolling.

The acid-etching process gives generally better results with the cast/rolled glass being used for bulk and lower-priced work. Double-side etched glass is the diffused reflection glass of choice for most bespoke framers, the leading brands being 'Inspiration NG' (Guardian Glass Industries). Single-side etching gives very good quality results for high-end framing but is more expensive to produce.

Examples are Reflection Control (by TruVue®) and Reflo (by Tegla). Cast/Rolled glass is mainly used for contract framing, photo frames etc.

Examples are Galleria (by Pilkington) and Glamatt (Glaverbel). Typically, diffused reflection glasses transmit 88-90% of visible light, reflect <8% and absorb 2-4%. UV filtration is similar to clear glass 45%).

Q What's the Difference Between Inspiration NG, Glamatt, GM Reflection Control, GM WaterWhite Reflection Control and TruVue® Reflection Control?

They are all diffused reflection glasses, designed to allow a wider viewing angle under difficult lighting than would be possible with clear float. Glamatt is produced by drawing the molten material over patterned (stippled) rollers. It is aimed at the bulk, contract end of the framing trade. Inspiration NG (formerly Velglas) is clear float with both surfaces etched (using hydrofluoric acid) to give a pleasant, lightly stippled effect. This type is the most widely used diffused reflection glass in framing. It does the job, but should be used on, or very close to, the artwork to reduce greying and loss of contrast. GM Reflection Control and TruVue®'s Reflection Control are clear float with one side (only) etched very finely indeed. It is a 'top-end' product (about 30% dearer than Inspiration NG) but can be used over double mounts and gives hardly any contrast loss. GM WaterWhite Reflection Control is produced in the same way as GM Reflection Control, however colour reproduction is improved through the ingenious use of a WaterWhite substrate.

TOP

Q What is Safety Glass?

Glass altered in such a way as to reduce the risk of personal injury to the end user and the public. There are two main types, toughened and laminated. Toughened glass is usually used where there is a high risk of impact and stress damage, as it is significantly stronger than plain glass. When broken, it disintegrates into small, relatively harmless, granular particles. Laminated glass is used for large panels where an element of security is required. Laminated glass is no stronger than plain glass but, due to the plastic interlayer, retains a high degree of structural integrity when damaged. Typical uses for toughened glass are: table tops, shelves, counter tops and panels, door and window glazing. Laminated glass is used in shopfronts, car windshields and high security panels. Both have limited applications in picture framing, but laminated glass can be produced to combat UV damage and, in very specialised forms, is widely used in Museums. See Denglas® (toughened and laminated), MIROGARD® and Rankins Glass in Links.

TOP

Q What is Low Reflection or Anti Reflection Glass (AR)?

Float glass with several layers of various metallic oxides on both surfaces. These coatings (known as Optical Interference Coating) dramatically reduce surface reflections by allowing very high visible light transmission through the glass. Visible light reflection is <1% and transmission can be well over 98% - particularly when a Waterwhite glass substrate is used. The same coating technology is employed for high-end spectacle, binocular and camera lenses. Designed to give optimum clarity to the artwork, these glasses should be used under good lighting conditions to give their full benefit. Used properly, they give huge improvements to image brightness, contrast and colour resolution. Not intended for use in harsh lighting, typical examples are: GM WaterWhite Museum, TruVue® AR and TruVue Museum®, Luxar and MIROGARD®.

TOP

Q What's the Difference Between the Various "Speciality Glasses"?

Whilst it can seem a bit complicated at first, all speciality glazing products are meant to give one (or more) of the following benefits over plain (float) glass:

a. To give improved 'viewability' under difficult lighting conditions: Inspiration NG and Reflection Control glasses.

b. To protect the artwork from UV light danger: GM UV ExtraClear, GM WaterWhite Museum, Conservation Clear,TruVue Museum® glass and Mirogard Plus.

c. To give maximum clarity and colour rendition under good lighting: GM WaterWhite Museum, TruVue Museum® and MIROGARD®.

d. To protect the artwork from physical damage in handling and transit and protect the public from possible injury: GM Art-Shield, Plastic(s) and laminated glass

Click here to see our Speciality Glass Quick Reference Guide.

TOP

Q What Does 'Waterwhite' Mean?

Waterwhite is the term applied to float glass produced from material with very low metallic impurity levels. Standard float glass can vary between a fairly strong green and a pale turquoise colour (looked at from the edge of the panel). For most applications, this range of colouration is perfectly acceptable but for critical uses (optical instruments, museums etc) a much lower colouration level is required. See Waterwhite Float and MIROGARD®.

TOP

Q Which side of SCHOTT MIROGARD WaterWhite AR® should be mounted towards the artwork?

It does not matter, all current SCHOTT MIROGARD WaterWhite AR® products can be installed either way.

Q Which side should UV filter be mounted (GM UV Extra Clear, GM WaterWhite Museum, Tru Vue Conservation Clear, Tru Vue Conservation Reflection Control & Tru Vue Museum®)?

With most UV products, the UV coated side should face the artwork (i.e. the inside of the frame). On all stock sheets of TruVue® Conservation products (Conservation Clear, Conservation Reflection Control, Conservation Perfect Vue and Museum® glass) the necessary information imprinted on the edges of the sheet, alternatively for smaller cut to size pieces or offcuts, you can inspect the glass by looking along the flat edge of the glass and look for ripples often referred to as the ‘orange peel effect’, this is the UV coated side. With GM UV ExtraClear telling the difference is harder, as we aim to produce a smooth finish (without the orange peel effect), therefore we recommend the use of a marker pen. Mark each side of the glass with the pen, and the coated side will ‘bead’ very quickly, place this side toward the artwork. GM WaterWhite Museum is simpler (again no orange peel effect), as you can frame this anyway around!

TOP

Q Is a UV filtering glass best for pictures hung in a conservatory?

The only glazing material to use in a conservatory or similar environment is a thick piece of plywood or hardboard. In other words, advise clients never to hang valued artwork in such conditions. Regular high levels of visible light (sunlight in particular) will still cause permanent damage to artwork - as will the wide range of temperature/humidity conditions also typically found there. If artwork is worth conservation framing, it should be hung out of the way of direct sunlight or even clear blue skylight and also away from radiators, heaters and damp conditions.

Sample Results on popular UV Products

TOP

Q Why do I need SCHOTT MIROGARD WaterWhite AR?

• Superior colour rendition . With SCHOTT MIROGARD WaterWhite AR, your customers experience art as its artists intended. Original colours and textural details shine through, true and vibrant. With this amazing glass, you needn’t worry about affecting the colour of your carefully selected matboard or the look of your customers’ art.

• Superior reflection control . SCHOTT MIROGARD WaterWhite AR is the perfect anti-reflective glass, virtually eliminating annoying reflection and glare. With less that 1% reflection, gone is the mirror effect from standard picture framing glass.

• Superior optical properties . SCHOTT MIROGARD WaterWhite AR provides the ultimate in clarity regardless of the number of mats or the depth of a shadow box. There is none of the distortion you see with etched, non-glare picture framing glass.

• Superior light transmittance . SCHOTT MIROGARD WaterWhite AR transmits 98.5% of visible light. Normal glass transmits only 90% of visible light. The human eye can detect differences in light transmission as low as 1%! Artwork looks brighter.

• Superior handling and care . The patented anti-reflective coating applied to both sides of the glass is as easy to clean as ordinary glass. No special cleaners are needed, no handling with white gloves.
   
• Superior value . SCHOTT MIROGARD WaterWhite AR completes the job your framing begins. It makes possible the perfect presentation of your customers’ treasured art.

TOP

Q Why do I need to use the New GM UV ExtraClear?

• Superior UV protection . GM UV ExtraClear by Glass & Mirror blocks over 98% UV radiation in the 300-380 nm range. Coated on one side using the very latest technology, you can be sure your customers’ art will be protected from the ravages of UV light.

• Superior colour rendition and optical properties . The coating process for GM UV ExtraClear by Glass & Mirror eliminates optical distortion. Neither you nor your customers will ever perceive roller marks or annoying orange peel effects. The art’s colours and details are presented as they are meant to be seen.

• Superior handling . GM UV ExtraClear by Glass & Mirror is UV-coated on one side and the patented coating is harder than all competing UV Clear products. And you’ll never have to wonder if you’ve got the right side against the art as each sheet (and cut size piece) is clearly labelled. It comes to you cut, washed and boxed in two popular sizes (48”x36” & 60”x40”).

• Superior care . You will be amazed how easy it is to clean this new glass. Just wipe fingerprints and smudges off the glass with a clean cloth and a mild detergent. Nothing is easier. Your customers will enjoy many years of exceptional performance from GM UV ExtraClear by Glass & Mirror.

• Superior value . By recommending GM UV ExtraClear by Glass & Mirror, you distinguish yourself and your shop as providing your customers with superior products, value, service and guidance.

<< Back to FAQ index