Re: Moulds

Nope, you got to read what has already been written.

hmm this sounds familliar...

read any post saying hydroperm.

Liam

"Some hilights from the exact question I asked about 2 weeks ago"

Hydroperm

1/32 milled fiber, (from a fiberglass user , Not cabosil I use about a handful when I make a bent panel for a lamp cover the surface with the plaster about 1 - 1 1/2" thick. Dry it for 4 hrs @ 200 deg F. then fire it up to 1300

The mold will be "done" and ready to come off the original in 25-30 min I start with a bowl of water, mixing bowl, 1/2 full of water, maybe less, shake the plaster in, continuously, about 1/2 to 2/3 of the way of what I figure will be the end, I grab a handful of the fiber and sift/shake/dump it in with the plaster and then continue adding plaster until it stops sinking in the water. Let it slake for a few minutes, 3-5,+ then use a whhip and mix it up

like I said if it is too thin, (thin pancake batter) let it sit for a couple of minutes. To thick, like peanut butter, throw it out and start over. Heat up a large jar of Vaseline, ( or dollar store equivelant) in a pan of water, when the stuff turns fluid, dump it in a coffee can and add Turpentine, equal amount, plus a little(for evaporation) mix the plaster pretty much like any other, adding the fiber, medium consistency, your spatula doesn't quite stand in it

1350 with most opals Yup, don't drape over, make a mold to slump into. Unless you go terribly high,(and 1400 is!), it will bend just fine and leave no marks.

Make a mold on the opposite side of the panel so it slumps into the mold and you will have no marks, drill a hole, as you found out, in the deepest spot, and fire to about 1265. Should be just dandy.

Hi Liam, thank you for your kind help to another artist. Elaine

Javahut is the guru of plaster molds, but he just went through a big teaching thing with me so I imagine he's a bit weary of the topic.

If you are looking for a book, he says check Dan Fenton's.

Lundstroms book 3 is all about it too. I've thumbed through it but never actually read much in it.

Learned the hard way: slum into, not over, cook fast after 1200 to avoid devit. but not to fast under 1200 to preserve the plaster. It will take you 3 times to do everything the right way.

Good preportions by volume are:

1pt, water, 2pt plaster. +milled fiber Good durable mold for smoother surfaces

1pt water, 1.5 part plaster + milled fiber, less durable mold, good for very fine detail, but if you take it up to the high temps you need to pick the detail up on glass, you may break the mold, and fiber glass melts around

1500, so you loose any merit it gives in strength at fusing temps.

Liam

Hi Liam, You are so helpful thank you. I know I could do a mould with fired clay as I have worked with clay for over 30 years, doing sculpture & pottery but it's nice to do other things as well. So for the last few months I am playing around with glass. Elaine.

I love clay for molds. Bisque fired stoneware is great. It doesn't shrink as much as steel or glass on cooling so it's great for slumping into. For slumping over, use steel, since it will contract an pull in from the glass drapped over. Or use clay but make sure the sides arn't so steep that the glass squeezes down on the clay as it cools. Kiln washing can be tricky on both so I like to use an airbush, with a very large aperature so it doesn't clog up. I'm a new fan of plaster though, since it needs no kiln wash, thanks Javahut. I'm not comfortable with going to fusing temps with it, but its great for slumping.

Liam

I'm a Java disciple as well, but I have never been able to get the fiber. I have to say that the Hydroperm works just fine without it.

1/32 fiber source

Let me know what you want and I will disperse as needed. $3.50 per lb is nuts. Or if your selling it, good profit.

Typically a single use plaster mold is made by mixing equal parts of #1 pottery plaster and 325 mesh silica. Hydroperm seems to be a popular substitute for the pottery plaster but I don't like it as much. Set up your model in a retainment ring making sure it is anchored to the base and seal all the edges along the ring with hot glue; clay may work but you'll find out soon enough that hot glue is better. In a large container put water to about 1/2 the anticipated volume. Now, using a flower sifter, sift the pre-mixed plaster/silica into the water SLOWLY! As you increase the mix the plaster will be absorbed more slowly. Keep at it until the plaster stays on the surface with little lines running through it. Try to get that surface as level as you can with your sifting. Go away for three minutes, or go apply separator to your model.

The next step is controversial and that's the mixing part. Some books say to use an electric drill with a special blade, and if you do you are sure to whip the mix into a froth which will leave plenty of air bubbles. There's another thread going about all this. I mix by hand. Roll up my shirt sleeve and go to work. I like doing it this way because it lets me feel the lumps and squeeze them out. I don't get bubbles this way either; no lumps, no bubbles = better finished product.

Plaster needs to dry before you use it. Depending on the size of the mold I may let one dry for several weeks. If it isn't too big, demold after a couple of hours and set it on top of your kiln while you do several firings. It will still need kiln drying and you do that by putting it in the kiln at 50 degrees per hour to 225 and holding it there until it's dry. How long is that? Well I program for about three times longer than I think I need and then check it by using a mirror over one of the peep holes. If you get condensation on the mirror, you ain't done yet. After that, you need to go to 325 to get out all the chemically bound water; hold there for 1/3 the time you spent at 225. Finally, go up SLOWLY to 1200 for the final curing (100 dph works well) and hold there for about the same time you held at 325. Beyond that, the mold is cured and your only consideration is the glass.

This is a conservative schedule which others may say takes too much time. Well, considering all the time you've got in making your model and getting it into the plaster, doesn't it make sense to play it a little safe?

Good luck, Jerry

Ela>Can any one in the group give me a recipe for making a high temperature

Nice words, Jerry,

You could write a book about your methodology. Very well researched, tested and written. The best and most complete information on making a mold that I have read. Into the file you go!

Hal

Thanks Jerry but who has the time for all this, and still be able to make a profit? I put paper tape around my piece, mixup Hydroperm with my wifes old hand mixer, and pour it on about 1-2" deep. About 30 minutes later the tape comes off and the glass separated from the mold. I either let it dry overnight, in the sun, or about 200 degrees for a few hours and it's ready to fire!

On the link below is a picture of cast leaves. That went from concept to clay model, to plaster/silica mold, to glass loading, to firing all in about 3 hours. A couple hour hold in the 200-300 range after the glass was in the mold worked just fine. Just make sure to vent the kiln.

Speaking of venting of the kiln, hoiw do you vent that big box of yours? Got a hole and plug in the top?

Right now I just leave the bell 1/2" off the bed. This was an oversight on my part. I have work to do under the bell soon. I'm going to trim the frax from 4" to 2" thick on the lower 4" of the rim. This will allow the large fiber kiln shelf to fit inside. The shelf was given to me after I built the bell. While under there I will install some sort of vent on the side wall at the top. Probably one each end. Or maybe a SS tube with holes that I can feed low pressure air. The only thing holding me back is that I haven't welded my safety chains on yet and I'm not about to get in that mouse trap without safety devices.

In another thread it said something about you being everywhere. A few weeks back I saw Elvis, Jimmy Hoffa, and Javahut in the parking lot of a

7-11 in Boise Idaho. When I tell people about it they say "There's no way you saw Javahut in Boise".

The only thing holding me back

No guts, no glory, ( I wouldn't do it either!)

Only the shadow knows....... nad he knows the perch are starting in Lake Erie, the fall Walleye are at Huron, Ohio, in Lake Erie, and the Lake Huron Salmon are getting into the rivers. and the steelehead are fast approaching. Michigan is a great place in the fall!

Indeed it is. I haven't seen one cider mill here in Utah and perch are considered trash fish. It's been almost 10 years since I was in Michigan in October.