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Urgent HELP needed
Posted: Mon Apr 15, 2013 12:56 am
by lorwolff
My kids are here for a couple of days, and want to try an art project that starts by heating rocks in the oven to 350 degrees.
Do I need to fear them exploding when heated??
Any advice would be appreciated,
Thanks,
Loraine
Re: Urgent HELP needed
Posted: Mon Apr 15, 2013 1:32 am
by JamesL
Do a You-Tube search for "Exploding Rocks" and you will see some kids heating rocks over a camp fire. They do "pop" or "explode". I have read that some rocks that are heated aggressively will crack, shatter, etc. Weather that's from internal moisture or the kind of rocks they are, I'm not sure.
Re: Urgent HELP needed
Posted: Mon Apr 15, 2013 7:47 am
by Brad Walker
If a rock has moisture in it, it will explode when heated.
If a rock does not have moisture in it, it will not explode, but it might crack anyway.
Most rocks have moisture.
(Not sure why this was urgent, by the way. Urgent is when your kiln is exploding, not a couple of rocks. <grin>)
Re: Urgent HELP needed
Posted: Mon Apr 15, 2013 8:39 am
by Valerie Adams
Invert a stainless steel bowl over the rocks so if they break apart in your kiln, they'll be contained.
Re: Urgent HELP needed
Posted: Mon Apr 15, 2013 8:52 am
by Bert Weiss
Sandstone is the most famous exploding rock. I have tried to fire granite, but that did not go well. It cracked.
Re: Urgent HELP needed
Posted: Tue Apr 16, 2013 2:04 pm
by Glass Fever
She's asking about heating to 350F in an oven, not firing at high heat. I think you should be OK at 350. If I was going to do this I'd put them in the oven without preheating.
Re: Urgent HELP needed
Posted: Tue Apr 16, 2013 2:47 pm
by Brad Walker
Glass Fever wrote:She's asking about heating to 350F in an oven, not firing at high heat. I think you should be OK at 350.
Why? If the rocks have moisture in them, the water would turn to steam long before you reach 350.
Re: Urgent HELP needed
Posted: Tue Apr 16, 2013 4:05 pm
by lorwolff
Thanks everyone, I apologize for saying 'Urgent'..., you're right, I don't want to cry wolf. (But when it comes to grandkids, I get crazy and over-zealous.)
Anyhow, we the rocks in the toaster oven, and none of the rocks were over 3 inches in size. 350 degrees is not really very hot. After a minute or two out of the oven they are not too dangerous should a kid bump or touch it. Important when planning a project for 5-6 year olds. With supervision it will be a good project for them.
Thanks again, Loraine