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I'm curious to know if any glass casters on this board have used hemp twine or cord as an organic burnout material. Even if you haven't used this, any thoughts from experienced casters about potential viability?

You could destroy the inside of your kiln if you get a big fire inside.

How so ?
Jim

Then I could find an alternative means than kiln for burnout.

jim simmons wrote:How so ?
Jim

Fire can be very hot, which is hard on elements.

Back in the early 80's my girlfriend was a beginning jeweler. She cast a silver moose, using the lost plastic toy moose method. She burned out the little plastic moose in a kiln. It caught fire and almost ruined the kiln, but it survived. The kiln, of course, was not hers.

Thanks all for your input. I'll be sure not to use the 'lost plastic toy moose' method!

Plastic is not the same as hempen twine. For one thing, most plastics aren't organic--many twines are--and if the plastic moose is solid it'd be rather dense and take awhile to burn out (assuming there's enough oxygen around for that). I could see a nice, long, oily petroleum fire, about like burning out petroleum-based wax. Hempen twine, on the other hand, is probably going to burn fast and hot, so it wouldn't be as much of a problem.

For the record, I use organics in mold mixes whenever I have an area of the mold that needs to be weakened, such as a multi-way curve where the glass is going to contract in on itself as it cools. If the mold stayed strong in that area, the glass might crack as it contracted. So I mix old leaves, chopped twine or rope, stale bran cereal, just about anything that won't expand when it gets wet/warm (if it does, it can actually break your mold).

The organics will burn out between 700-1000, leaving a structure that looks strong on the outside but is a bit like swiss cheese in the weakened areas. When the glass starts to contract the plaster can collapse into the hollow spaces instead of having nowhere to go.

plastic isn't organic? it's a hydrocarbon. organic chemistry is most anything containing of carbon.

I stand (very) corrected. Yes, petroleum products are hydrocarbons and therefore contain carbon and are therefore organic. Apparently I have overdone the hippie bit because I have forgotten my organic chemistry and have apparently started using the term "organics" to mean "anything that doesn't contain "petrochemicals." Uhm...ooops.

What I MEANT was... plastics and other petrochemical products I've used tend to leave a sludgey, nasty residue behind in the mold when you heat them to those temps. Hempen twine and similar substances generally burn out completely or at most leave a little light ash behind.