Spectrum Green Devit

janine · Post by **janine** » Tue Feb 24, 2004 2:42 pm

Hi to everyone:

Does anyone know if Spectrum green 121SF is more susceptible to devit than other colours???

I am experiencing devit but only on this green. I took two rather large pieces out this morning and there it was. One of the pieces is multicoloured strips of blues and green. It looks great, except for one small strip of the green has splotchy devit beginning in the middle of the strip, but not covering the whole strip. There were several other pieces of the same green from the same sheet but nothing on them.

The other piece is made up of various sizes of spectrum green 121SF squares and the devit attacked it randomly and in various degrees of strength.

My firing schedule is the same as previous firings containing this green when no devit occurred. I do not grind the edges and I cleaned each piece thoroughly with vinegar and water.

My firing sched. is this 350 - 1000 - 0/ 300-1160- 15 / 300 - 1455- 10/ afap-1000-8 / 300- 955 - 20 /200 - 800 -0/ etc.

I have a bunch of other pieces containing this green ready to fire, but have now lost confidence in this colour.

From reading the archives it looks like I could either try an etching cream, sandblast an use an overspray to remove it. I'm thinking I will try the etching cream first, as that looks to be the easiest at this point???

Thanks for any feedback.

janine

Geri Comstock · Post by **Geri Comstock** » Tue Feb 24, 2004 9:43 pm

Etching cream may work just fine. I used to do that to remove devit.

More recently, I've had success at "covering up" devit after the fact by applying SuperSpray overglaze, but not everyone has reported the same good results I've had.

Good luck!

Geri

janine · Post by **janine** » Wed Feb 25, 2004 2:30 am

Geri:

I have the cream but haven't tried it yet. What I did do was polish the piece with Walters Blue Paste (for polishing metals to a mirror finish) and a variable speed orbital sander I stuck in a vice. It worked really well. It is really hard to tell where the devit was. It looks like I got away without having to firepolish.

I'm wondering though, that since I didn't sandblast it or etch it off that some of the crystals may still be lurking there and if this will cause them to grow again if I did firepolish or during the slump.???

Thanks so much. Janine

charlie · Post by **charlie** » Wed Feb 25, 2004 10:44 am

devit can't form at room temp, so if you can't see it now, you won't unless you heat it up again.

janine · Post by **janine** » Wed Feb 25, 2004 1:06 pm

So are you saying then that the devit has to removed 100% (either by sandblasting or etching) or it will return upon slumping????

janine

charlie · Post by **charlie** » Wed Feb 25, 2004 1:17 pm

janine wrote:So are you saying then that the devit has to removed 100% (either by sandblasting or etching) or it will return upon slumping????

janine

it's possible. it depends upon the specific glass, the temps you use, and the time. the devit range is different for each type of glass. i tend to get devit a lot on opals, so use borax on almost everything to prevent it. if i get some on a piece, i blast it off, treat with borax, and fire polish. i tend not to get it on a slump, but it is possible especially if you're slumping in the 1225+ temps and holding for a long time.