Devitrification Question

[Kev]

Are there specific glasses that are more prone to devitrification, and knowing that, what steps can you take to try to avoid it?

[Stephen Richard]

"Are there specific glasses that are more prone to devitrification, and knowing that, what steps can you take to try to avoid it?"

OK. I will have a try.

Glasses that are formulated and tested compatible for kiln forming are less likely to devitrification than other art glasses.

Opalescent glasses even if tested compatible for kiln forming are more likely to devitrify than their compatible transparent counterparts.

Yes, you can fuse some of the transparent glass made by a single manufacturer - Spectrum transparents and especially the water glasses are most often compatible within certain limits.  But you will find that the edges show devitrificatiion almost always.

You can clean very well and hope for the best, or you can clean and then use a devitrification agent - normally a flux or low firing glass in suspension - and spray or brush it on.  If it is one of the low firing glasses in suspension, make sure you put it on before taking it to the kiln, as it will stick to other things when fired.

Another method is to avoid staying in the devitrification range of temperatures very long - both during temperature rise and cooling.

A description of what devitrification is, is given here:
http://glasstips.blogspot.com/2009/08/devitrification.html

The temperature range in which devitrification occurs is indicated here:
http://glasstips.blogspot.com/2009/05/devitrification-temperature-range.html

A homemade devitrification solution can be found here:
http://glasstips.blogspot.com/2009/07/home-made-devitrification-sprays.html

[Judy K]

Thank you Richard

[Becki]

Stephen, is there a right or wrong way to use devit solutions?  I've never had a problem with devit and have never used one but I've read that some have problems with them.

[Kev]

I heard they eventually wear off. Now is that if it's put in the dishwasher or stuff like that, or can you expect it to last a long time as a decorative piece?

[Audrey]

OK. I just read the link to the description of devitrification. I mentioned annealing, which I have heard many times before but have no clue as to the meaning.

[Kev]

Start a new topic in the regular fusing board with that question Audrey and it will be answered in that new post. This way we can keep all the information separate and together with the appropriate questions and will allow for easy indexing in the FAQ's.

[Stephen Richard]

Stephen, is there a right or wrong way to use devit solutions?  I've never had a problem with devit and have never used one but I've read that some have problems with them.

Smooth and complete coverage of the piece is the aim when applying devitrification solutions.  A soft brush, an air brush, a mouth atomiser and some even use a sponge - all these will do the job. 


As to problems, I don't know what they may be until specified.  It is a pretty simple process, but requires concentration to ensure the piece is evenly covered.  If it isn't, there will be areas of devit left after firing.

[Ian]

Kev
I remember reading somewhere that borax will eventually be dissolved by water so not to use on anything exterior
Ian

[Kev]

Good to know! Thanks

[Stephen Richard]

Kev
I remember reading somewhere that borax will eventually be dissolved by water so not to use on anything exterior
Ian

It is true that Borax is water soluable.  However, the borax has done its job by preventing the devitrification, so it does not matter whether it has or has not disolved, nor whether it is inside or outside.

Borax as a flux for paint in excessive quantities has the effect of corrosion on the paint or enamel it is mixed with.  It is not actual corrosion, just that its effects are like that.  The borax expands when wet.  The expansion is very little, but over time "pops" off the paint - the time scale is 50-80 years.  This happens on the inside of windows where the paint is.  So it is not an inside/outside issue, just one of moisture.

But this irrelevant in kiln forming applications to prevent devitrification, or even to correct existing devitrification.  The subsequent possible disappearance of the borax will not matter to the appearance of the piece.  It has been reported that borax covered sushi dishes going through diswasher cycles in a restaurant for years show no devitrification after the presumed disappearance of the borax.  In fact, the propritary devit solutions that contain lead would not be applicable in this food containing situation.
Steve

[Kev]

Well that's good to know..thanks!