Topic: frit

[krsilber]

Frit used simply as batch colorant?  Better way of adding the materials than separately?  Been looking at patents.

[Sklounion]

Frit - glass in fine granular form, often made by heating and then dropping glass
into cold water to aid in its break down into fine granules.

Transformation temperature - is actually a narrow temperature range above which
glass behaves like a liquid. It is a result of raising the temperature of the
glass to the point where its tendency to flow is dramatically increased.

(Source: Glossary from "Mixing with the Best" written and edited by Angela Thwaites. 2002 Published on CD-Rom. ISBN 1 874 175 84 5)

Angela is a leading contemporary glass-maker, and the only British artist in glass to have studied with Stanislav Libensky.

Another good source giving contemporary usage of terms is Charles (Charlie) Bray's "Dictionary of Glass: Materials and Techniques" 1995, 2001, ISBN 0812233573 published in the UK by A&C Black, and in the US by University of Pennsylvania Press 1995.

regards,

Marcus

[krsilber]

Thanks, Marcus, for the additional definitions and references.  I just bought 3 or 4 glass books; maybe I'll see if my library system has these for now (or the Bray, anyway).  Does Thwaites mention what frit is used for?

I just found another definition, this one in Julian Henderson's The Science and Archaeology of Materials.  It is on page 38 in one of the Google books "previews" that shows much, but not quite all, the book; there are some other interesting parts that are shown besides this one.  http://books.google.com/books?id=p9xJ-VpUuNkC&pg=PA24&source=gbs_toc_r&cad=0_0&sig=ACfU3U16ZtJu-J6Ytel89Memw94beCtrmg#PPA38,M1
"The basic procedures of glass-making can involve five main steps:  (1) the selection and preparation of raw materials; (2) making the glass involving fritting the raw materials; (3) mixing the 'batch' and melting the glass; (4) working the glass to form the glass objects; and (5) annealing the objects....The most enduring ancient glass chemical composition was soda-lime-silica...The alkali (soda), a silica source and a lime-rich raw material are heated together initially to form a 'frit', a semi-fused granular material.  True frit is defined as the semi-fused primary raw materials of glass-making (Henderson 1995:  99), in which the formulation of glass has been arrested; it occurs at relatively low temperatures (see Figure 3.12).  ...The hot frit may be thrown into cold water where it breaks apart.  This procedure may be repeated several times.  The main reason for fritting glass raw materials is in order to rmove any impurities, especially gases which are derived from the breakdown of carbonates (releasing carbon dioxide) and sulphates/sulphides (releasing sulphur dioxide or trioxide); another reason is to reduce the number of gas bubbles in the glass-melt."

Of course, I don't offer this definition because it is somehow more correct than others, it's just an alternate one.  I don't know what is meant by semi-fused.  A patent I just read talks about fritting as simply putting glass in water to break it up (discussing a low-fire glass enamel/glaze).  There are enough of both types of definitions that they must both be correct; the more elaborate one seems to be based more on historical procedures.

[krsilber]

Just a couple notes to follow up on the frit business.

A while ago there was discussion of Pyrex on the board, and while I was looking at the Corning site for info about it, I came across some references to fritted glassware.  This page is about selecting and using it:
http://www.corning.com/Lifesciences/technical_information/techDocs/frittedglass.asp?region=na&language=en
Apparently it is used in filtration (a use I'd come across before); perhaps that's because it's not totally fused?  Still a little con-fused about that.

Then there is this patent:
http://v3.espacenet.com/textdes?DB=EPODOC&IDX=WO2007087125&F=0&QPN=WO2007087125
part of which reads,
"[0044] The batch materials shown in Table 2 were weighed out, mixed thoroughly and placed in a 4 inch platinum crucible in an electric resistance furnace set to a temperature of 2,600<0>F (1,427[deg.]C) and heated for 2 hours. The glass melt was then poured into water at room temperature (referred to as "glass fritting" in the art) to produce a glass frit. The glass frit was dried in an annealing oven set to a temperature of 1,100<0>F (593[deg.]C) for 20 minutes. The glass frit was placed back into a crucible, and the crucible was placed in an oven set to a temperature of 2,600<0>F (1,427[deg.]C) for 2 hours. The glass melt was cast on a metal table"

I wonder why the double melting, same ingredients, same method.  Any ideas?  (Whew, platinum crucibles!  Those must cost a pretty penny!)

[krsilber]

Was just reading bits and pieces of this online book, A Treatise on the Progressive Improvement, and Present State of the Manufacture of Porcelain and Glass (1832, George Richardson Porter) and came across a passage about fritting that tells nicely what the process did (page 154):

In the first place, it expels all moisture from the materials, the presence of which would hazard the destruction of the glass-pots.  Next it drives off either wholly or in great part, the carbonic acid gas from the chalk and alkalies employed, by which means the swelling of ingredients in the pots is either prevented, or moderated within safe limits.  This calcination has the further advantage of destroying all carbonaceous matters that may be present in the materials.  But the principal object of previous calcination is, that a chemical union may be effected, or at least commenced, between the silex, the alkali, and the metallic oxides.  Otherwise, at the heat of the working furnace, the alkali would fuse, and its comparative levity would cause it to take its station at the surface, while the other ingredients would suside towards the bottom.  The uncombined alkali would, in this case, after acting upon and injuring the substance of the crucibles, be, in great part, volatilised and lost; and a portion of the sand would remain unvitrified, while the glass actually produced would contain an excessive quantify of silica.

Thes observations do not apply to the preparation of materials for making flint glass, the fusibility of which is much greater than that of other descriptions, owing to the presence of its large proportion of lead.

Perhaps these days the ingredients are refined enough that fritting isn't necessary, and the term has come to mean something else?

[Frank]

Interesting re-reading this thread and getting it all in one dose, the evolution of the words usage is clearer. That other term Transformation temperature sounds to me like an invention for a specific scientific term (I forget) that was used to describe when a material changes state at a specific temperature. I recall we did experiments in the Physics lab with various materials including water in order to measure the temperature at which the material goes through changes... solid to liquid, liquid to gas and vice versa. But the scientific term has got trapped in those fritting grey cells.

Also partly fused can certainly apply to at least much modern art pate-de-verre as well as the sintered glass used for filtering. The end result being a porous material that I have found to be the most effective material for filtering fish tank water. It comes as either coarse granules or short lengths of tubing and is usually an off white colour - the tube makes a highly efficient 'fine' nail-file too.

But defining which is the correct version of the meaning is not possible without the context. To translate terminology to that used in a different context is only going to lead to confusion... so in other words it is better to use the term as it would apply to the period or area of discussion. Dictionaries deal with this by just listing all the different usages and we should follow that establish guideline. Having all the different refereces as above is thus very useful.

[Cathy B]

Phase change?

[Frank]

Thanks Cathy. Just looked that up, and the term I tried to recall was latent temperature. I guess that the term Phase transition/change was not around when I was at school. What I mostly remembered was that the latent temperature of water was fractionally below boiling point and that it a 'strange' state when the water is neither liquid nor gas.

Reading up on it today, it also has strange optical effect... but to take that discussion further would be a cafe topic.

[krsilber]

I think the transformation temp. is that at which molecules change their structure, with a simultaneous change in volume, and heat is either evolved or absorbed.  I don't think there's necessarily a phase change though.

What I mostly remembered was that the latent temperature of water was fractionally below boiling point and that it a 'strange' state when the water is neither liquid nor gas.

Reading up on it today, it also has strange optical effect...

 

That's sounds interesting!

"the sintered glass used for filtering."  This is what I was talking about when I mentioned the Corning info about fritted glass.

"Also partly fused can certainly apply to at least much modern art pate-de-verre "  Is that before or after it's been "cooked"?  (I should know this!)

I agree that the meaning of frit is these days context-dependent.  It doesn't seem to be a strictly historical term though, based on the many modern definitions describing frit as partially fused glass ingredients.  I still don't know just how the term is applied by glassblowers these days, since Adam said that ground glass is more often called grains and powders than frit (in the UK, anyway).  Incidentally, there's something called "pebbles" on the Kugler site that looks more like it could be partially fused glass than it does like regular glass, but I don't know if that reflects reality.

[chopin-liszt]

 

Sorry, I really can't read all that, but my tuppence worth is that I thought it mostly referred to unwanted bits of stuff which contaminate a gather, either from impurities within, or even bits of stuff accidentally picked up from the marver.

It's also a useful, clean swear word, as in ""Fritting prunts!"