PATE DE VERRE mold filling questions

[Ted Metz]

I am about to cast fine frit into a plaster/silica open faced mold. The resulting casting will be 6"X14"X2" thick. The mold has dried for several weeks and has spent 40 hours @ 165 degrees in a vented foodwarmer. (see previous post about foodwarmers if interested)

The books I have studied say to bring up the temp of the mold slowly to around 1200 degrees, cool, and then fill the mold with frit. I understand curing the mold, the need to remove chemically bonded water, and the need to go slow.

My question is: Why can I not just fill the mold with frit and then proceed to cure the mold and move right on to casting temp? Won't the slight amount of wax residue just vent through the frit? There will be some low areas in the mold where I will apply colored frit mixed with gum arabic. Does any one see any reason why I shouldn't cure and cast all at once?

Thanks. Ted

[Brock]

What wax residue? Can't you clean it all out, as it is an open faced mold?
Anyway, yes, I think you can just fill it and go. We did it at Pilchuck with molds holding up to 40 lbs. of glass. We went up to 200 slowly, then held for 6 hours, then on with a conventional casting schedule. These molds were fresh, coupla days old, with no drying, or pre-firing. You may have eliminated the need for the hold at 200, with your drying, but I'd be inclined to do it anyway. In casting, conservatism is a good thing. Brock

[watershed]

the other reason to dry is that you may get less cracking of the mold, if the mold is dried slowly. Now that you have some dry ones, try a wet one, and check the difference.

Greg

[Ted Metz]

Thanks Brock and Greg,
Brock, there is no visible wax residue. I just figure there must be some remaining film on the mold, maybe not. Thanks for the quick response, I will fire it up in the morning.
Ted

[Brock]

Thanks Brock and Greg,
Brock, there is no visible wax residue. I just figure there must be some remaining film on the mold, maybe not. Thanks for the quick response, I will fire it up in the morning.
Ted

Yeah, I think you're right, even on a thoroughly steamed mold, there seems to be a wax smell as you fire it. Brock

[Delores Taylor]

The books I have studied say to bring up the temp of the mold slowly to around 1200 degrees, cool, and then fill the mold with frit. I understand curing the mold, the need to remove chemically bonded water, and the need to go slow.

I use holds at 250, 350 and 1000 (physical water, chemically bound water and quartz inversion as points to hold to avoid cracks in the mold)

My question is: Why can I not just fill the mold with frit and then proceed to cure the mold and move right on to casting temp?


I put my wet molds on a sand bed and then use the above referenced hold points. If you cure at the various hold points for long enough you won't get cracking.

Won't the slight amount of wax residue just vent through the frit?

Wax might cause blow outs so make sure your mold is as steamed clean as possible.


There will be some low areas in the mold where I will apply colored frit mixed with gum arabic. Does any one see any reason why I shouldn't cure and cast all at once?

Works for me and your painting will be far easier with a wet mold not a dry mold.

Thanks. Ted

[ellen abbott]

I realise I am a little late here, but for future...we don't pre dry our molds at all. Just ramp slowly with holds at certain places...my partner does this so I can't give you particulars. In fact, I find it easier to place my frit when the mold is not completely dry. Otherwise the mold wicks away all the liquid from the gum arabic solution and I find it hard to manipulate the frit into place. We usually fill our molds within in a day or two of making them with no attempts at drying. Slow is the key. Our molds are usually cracked somewhat when they come out of the kiln which makes for easy removal, but the cracking doesn't occur at the critical stages when the frit will flow into them.

E

[Ted Metz]

Thanks Delores,
I hadn't considered quartz inversion with only 1/2 of the mold material being silica.
I will use your hold points and see how it goes.
ted

[Ted Metz]

Thank you too Ellen,
Everything I have read talks about dry molds. This is refeshing to hear the opposite. I am wide open to trying all the possibilities I can. I will fire wet next time and see how it goes. How large are your molds? Or, how much do the casting weigh?
ted

[Lauri Levanto]

LAst summer I was at Päivi kekäläinen class for *thin*
pate de verre.

She told to use wet mold, it was kept moist during
packing with water and frit pate. The inner surface
was then painted with dilute glue.
The piece was then immediately fired in wet mild. Slowly!

Ted was asking for *thick* pate de verre.
I don't think it is different from kiln casting.

Casting molds I pre-fire to 250 C ( chemically bonded water). Then I inspect the mold for cracks,
fill the mold and firequite fast but
soaking for Quarz inversion around 572 C.

-lauri