What's happening with float glass? v2

To paraphrase a popular TV advert, ‘float glass aint float glass’. Unlike with oils, where some oils may work better than others, when it comes to kilnforming some float doesn't work at all.

In addition to the traditional float glass with tin on one side and nothing on the other, float is now available with soft or hard coatings, with names such as low E or self cleaning, which can drastically affect the way it responds to re-firing and make it completely useless for that purpose.

The Australian Trade Practices Act places an obligation on the supplier of a good to supply an item which is suitable for the purpose, or which conforms to the customers requirement or specification. Should that not occur then the consumer has redress against the business from whom they purchased the good and to whom they paid their money; not with any other person or organisation higher up the supply chain.

Few people in the glass distribution industry understand the niceties of warm glass working so it makes sense for the kilnformer to spell out their requirements in detail. This means that if you are to receive glass suitable for kilnforming then you must make your requirements clear down to the last detail.

• Always place written orders.

• Specify either plain float or low iron glass free of organic or inorganic coatings.

• State that the glass is to used for kilnforming and that Low E, self cleaning or other treated glass is not acceptable.

• State that the pieces are to be cut from the same sheet or from the same block if that is appropriate.

• Ask the source or maker of the glass you are receiving. This to allow you to be able to request or reject glass from the same maker in the future.

All of the above should make your requirements clear to your supplier.
Traditionally a reasonably competent kilnformer could expect a 90% to 100% success rate when using conventional or low iron float. Because the demands of the architectural industry has seen new products introduced is no reason for the kilnformer to be supplied unsuitable product, nor for their success rate to drop.

Here’s a few matters to consider when placing your written order;

• Buy clear float in the largest size sheet you can afford or handle.

• Break it down yourself as far as possible. Ordering pieces cut to size is convenient but gives no guarantee as to the relationship of each piece to the rest.

• Educate your glass supplier about the special requirements of the kilnformer applicable to float; make them understand that you have an interest in who is the maker of the glass you are buying. Having sorted the firing problems, surely you would want your next order to be from the same source as the last.

• Consider the size of your supplier. Do they buy in bulk or only a few sheets at a time? And similarly for their sources up the line.
  
• Do a test firing before committing larger or more complex pieces.
  

• If ordering special shapes to be cut, request some of the offcuts so that a test firing can be done.

Clearly state your specific requirements and then assert your rights under the Trade Practices Act if they are not met.

Recent comments about problems with firing float include;

• devit appearing after only a short firing

• a loss of clarity or cloudiness of the glass after fusing supposedly compatible layers with the tin side correctly positioned (down on both layers)

• a corrugated or puckered looking surface after firing which may be likened to the inside of ones mouth after sucking on a lemon.
• float which failed to fuse at above 800 degrees C
  

It would be easy to write off such comment as being due to incorrect firing technique, incorrect identification or placement of tin side, confusion between tin bloom and devit, or numerous other causes not related to glass quality. However, as most comment has come from highly experienced sources it should not be so lightly brushed aside.

Information on ongoing changes to product and possible ways to identify them will be posted in the  About float glass

page from time to time.