Re: Moulds

Love the leafs.....

The interesting thing is that we all do what works for us. I don't like the way Hydorperm performs at casting temperatures; it gets less detail and is subject to cracking. Using a mixer has always caused bubbles for me so I don't do it.

If you've been successful with your method then the kiln gods have blessed you. I just did a free standing oriental dolphin where the mold was two inches larger than the model all the way around and it weight in at just under 80 pounds. If I had used your system of drying I hate to think what condition the mold would have been in. Using my system I've got a great piece.

Now, there is merit to what you've said. I do a number of small castings about the size of paper weights and those I pour and fire the next day. Either I set them on top of the kiln while something else is firing or I just go slow the first several hundred degrees and it works just fine. It all has to do with how big the mold is and how much you are willing to risk the work you've already done.

Thanks for giving me your perspective.

Jerry

For what its worth, to those who are interested:

Jerry, your method is time tested and has been used for eons, by a great number of people. It is considered by those who use that material as "the way it is done". Not a thing wrong with it in my book, except I have too many bags of too much stuff here now, and I have found that Hydroperm has a great many uses.

When I am doing kiln casting, I mix it up with the chopped fiber additive, and it works great for higher firings when Diatomaous earth is added, along with Kaolin clay. Get great detail at higher temps, and you go slow right from the beginning with no seperate drying time. Take it up slow and it works just fine, it is remarkably like plaster and silica.

Straight out of the bag, US Gypsum says it is rated for 1000 dg F, for those that are using it straight up, great, I did for a long time for one off molds. With the fiber added, (a binder, as all the authors call it) it can take to 1400 rather easily. Shrinkage is less that 1%, negligable unless you are doing large items then it is still small.

The bubbles discussed in the mixing portion: these are beneficial when doing a one off, with high detail, because the gases and air between the glass and the mold pass into the mold.

This is where Liam had trouble understanding why he had to drill a hole in the bottom of a slump mold, he thought that the air would go into the mold. IT will, IF you mix the plaster as US Gypsum recommends, which is by weight, and makes a very thin, fragile mold. You use the mixing paddle, jffy mixer, etc, with power drill and you do it in a container that will allow the plaster to swell to an additional 60% volume. That is alot of gain, and makes for a great mold that needs no venting, or nearly none, for slumping, or casting white metal into. For a more durable, I don't mix this way, the kitchen whip I use puts nearly no bubbles in, and certainly none on the contact surface.

There are just such a variety of ways to do somethng, anythng, in this medium we all enjoy, that it is impossible to say a particular method is better than another.

As Jerry said, this is what works for me, I use the heck out of this stuff, I bend glass every day, and for profit margin on hours worked, if I can get it out of here in less that 24 hours, I am happy. Hydroperm lets me do that.

For kiln casting and frit casting, I can use the same material, and just adjust it a little, great.

I will say, Hydroperm is looks very much like my mixed putty/grout and it does NOT work to cement a window, BELIEVE that!!

I'm a believer now, but it took a few tries. The duds make nifty paper weights. L.

. While the topic is still fresh, would you mind passing on the recipe for this? ramp? temp? hold? Diatomaous earth, from the garden store? I've never seen Kaolin clay, do I need to know any details on this, like mesh size or anything like that?

Thanks again for all the help Liam

I use the Hydroperm/Diatomatious earth (is the sand used in swimming pool filters), Kaolin Clay, from Ceramic supply House, I use the Formula in the Latest Dan Fenton book, I would have to look it up myself. At least I think thats the book, and I use a firing schedule from there also.

Just playing and learning the kiln casting stuff myself, so I go with what I am told works and adjust for my needs after .

It sounds like there is an archive somewhere, yes?

Dan Fenton's got 2 books. They both look good, and I'll probably buy both of them some day, but which one were you referring to? Check this link

With Jim Kervin, Patte de Verre and Kiln Casting, very interesting book, lots of info on mold stuff and schedules.

And just for the record, that book gets a whole lot more interesting after taking Dan's casting class. He's a character and is a big one for getting his students confident enough to try new stuff.

Jerry

Javahut wrote: