Glazing

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Overview

This section deals with the different glazing options available to the framer, including the benefits and applications of different glazing types, cutting and cleaning, plus additional advice on the handling of speciality glass.
With acknowledgements and thanks to Glass & Mirror. for providing some of the following information.

Contents



Glazing Types

Not all Glass is Equal

Choosing the right type of float glass for thejob can be confusing, but the following information should simplify that process. Officially there are only two types of float flass, 'Ordinary' (green) and 'WaterWhite' (colourless).
Note:It is inevitable that some 'brand names' will be used by other distributors or manufacturers, these are not intended to confuse, however if you are in any doubt, seek assistance or guidance in order to ensure you and your customers obtain the glass they seek.

The making of.... Float Glass

All glass is made from Silica sand (which is available in a variety of grades from green to colourless), which is headted to approximately 1100oC before being poured from a furnace onto a continuous bath of milten tin. It then floats on the tin (hence the name 'float glass'), spreading and seeking a controlled level surface. The thickness of the glass is controlled by the speed at which the slowly solidifying glass ribbon is drawn across the tin bath.
the continuous ribbon of glass then travels for about 120 metres throught a cooling Lehr ( graduated cooling chamber) until it emerges at room temperature. The product is perfectly flat and has virtually parallel surfaces.

Different glazing types are appropriate for different framing applications. Factors to be considered in order to choose the best glazing option for a job include: the value of the work (sentimental as well as financial); the lighting conditions in the room where it is to be displayed; safety regulations; weight of the finished frame; and budgetary constraints.

Standard (Float) Glass

Ordinary Float Glass is produced from Silica sand containing a large number of metallic impurities (namely ferrous oxide otherwise known as iron). When viewed from the side, ordinary float glass contains a strong green colour this is as a direct result of the metallic impurities. Often this isn't particularly notiiceable by the framer, however when placed alongside 'Low iron' or 'WaterWhite' glass there is a marked difference.
The green colour of ordinary Float Glass may change the colour of any mounts used, especially when viewed over a white or a cream mount.

It should be understood that ordinary float glass is perfectly suitable for the majority of framing jobs, however if colour is of paramount importance then you need to use a colourless (low iron) glass such as 'WaterWhite'.

Diffused Reflection Glass

Many framers avoid diffused reflection glass for the wrong reason, stating that it 'greys' the image.
Diffused reflection products must be given space within any workshop, as they represent the ideal product to be used when framing artwork that is to be positioned under 'harsh' lighting conditions (and some cases artificial lighting too), where more expensive 'Optical interference Coatings' would not be suitable.

Diffused reflection products have a textured surface. This can be achieved in on of two ways:

Rolled - This is the cheapest way to produce a textrued surface. Textured rollers imprint a pattern onto the surface of the glass whilst it is warm, in a similar way that bathroom glass is produced. These products are aimed at the cheaper, volume end of the market, and it is recommended that they be used directly against the artwork, or certainly no more than one mount away.

Acid Etched - This is by far the most popular way to achieve a diffused reflection finish. The surface of the glass is treated with acid in order to remove the smooth, shinny surface. On premium products you will also find that the quality of the etching is also greatly improved, offering a finer quality etch then you would normally attribute to ordinary diffused reflection glass or plastic products. This type can be used over multiple mounts, from 1 to 3 dependant upon the quality.


Typically both sides are etched; however recent technological advances mean that some manufacturers are now etching on one side. The reason for this isn't at first that abvious, but as one considers the reasons behind it, then the idea becomes much clearer! The side that faces the artwork need not be etched as reflections are not an issue on the inside of the frame, only the outer face is of concern and therefore it is only the outside that needs etching!
By etching the product on one side, the artwork may be seen more clearly than it would if it were etched on both sides, reducing greying. Therefore, you have greater flexibility when framing artwork, allowing multiple mounts to be used without too much loss of detail, improving the overall aesthetics of the image not to mention increased profits!

Ultraviolet Filtering Glass

Light is made up of differing wavelengths. For example a rainbow has different colours and each colour within the rainbow will have a different wavelength and each wavelength is measured in units, these are called nanometres. How large is a nanometre?

1 nanometre = 1 billionth of a meter (OR 1/80,000th of a human hair!)

The most damaging light is UV (or Ultraviolet) invisible light between the 200 and 400 nanometre range, this range of light is invisible. Despite being invisible to the naked eye it is powerful enought to induce photo chemical damage to organic material such as paper or fabric, resulting in loss of colour, yellowing, bleaching, darkening and embrittlement.
Ordinary Float Glass filters around 54% of the harmful range, however this is NOT sufficient to offer any degree of protection. Whilst UV protection may not be an issue in certain circumstances where UV is not sonsidered a hazard, there are still manyinstances where additional UV protection is still required. Below are some ideas as to when to choose 'UV protection' over a 'non UV product':

The image below shows the nanometre range, including which light is visible and invisible, plus which light must be controlled and how:

As you can see, light up to 200 nanometres is filtered by the earth's atmosphere.

Between 200 and 300 nanometres some protection is gained from ordinary glass.

However, between 300 and 400 nanometres a good UV glazing product should be used.

Over 400 nanometres light becomes visible, this is the violet / blue range. Although it is recomended that this level of light be filtered, to date it has not been possible to create an effective product that will filter this effectively. This is because to filter this range, a strong yello filter would have to be used to counter the blue light, which would leave the artwork looking very visible yello due to the filter. As this light cannot be filtered caution should be used to avoid hanging images in 'blue sky' or 'sunshine' areas.

The only truly effective way to protect valuable artwork from the 400 plus nanometre range is to block out this light, whouch could be done through the control of light coming into the building (such as that undertaken by museums).

The three most common ways to achieve UV protection are:

Flat glass - Coatings applied to the surface of glass, usually one side. UV coatings tend to be relatively soft and can be easily scratched, which is why they should be placed directly against the artwork, avoiding the possibility of damage from repetitive or harsh cleaning and handling. Coatings vary in quality and high UV ratings do not always mean best vieweing quality!


Laminates - In the majority of cases UV protection is achieved by using a UV filtering plastic interlayer (PVB). This provides higher UV protection than that of coatings and is invisible to the eye, furthermore laminates provide grater protection for artwork in the event the glass should be broken, which is why these are the product of choice for high end museums and galleries.


Plastics - Similar to laminates, the UV protection is generally impregnated within the plastic during production, increasing UV rating and viewing quality. These are ideal when images are to be transported or placed in public areas.


'Museum' Glass

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'Acrylic Glazing

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Storage

It is recommended that you store all your glass upright and in particular your Speciality Glass in its original packaging where possible.

Cutting Glass

Before cutting, remove any traces of Glass chips/particles from your workbench with a soft bruch. DO NOT drag or slide sheets of glass across the workbench or each other, ALWAYS lift sheets to re-position or measure them.
Use a cutter with a Tungsten Carbide Wheel of approximately 124o, lightly oiled. expand
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Cleaning Glass

Only use clean, soft, lint-free material for cleaning. Any proprietary ammonia free glass cleaner may be used. NEVER use abrasive cleaners, household cream cleaners or contaminated cloths.<Replace this text with information about this topic.>

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REMEMBER

THE COATINGS ON SPECIALITY GLAZING PRODUCTS ARE DURABLE AND STABLE WITHIN THE FRAME. THEY ARE LIABLE TO DAMAGE THROUGH IMPROPER HANDLING DURING STORAGE, CUTTING AND CLEANING. BY FOLLOWING THE GGUIDELINES PROVIDED HERE AND BY OTHER MANUFACTURERS, YOU WILL HAVE MANY YEARS OF TROUBLE FREE FRAMING.