When I first started casting I thought using plaster would be a great idea until I poured molten aluminium into the plaster mold. After many hours of drying in a oven the plaster still erupted like a volcano and lucky for me I was not burnt like my subscriber in his video. Have a look at 7:37 face shields are a must have item in the home foundry.
I had a similar experience as a boy attempting to cast into plaster. I was forunate that I suffered no significant burns, but that was sheer luck.
Yup! I like a dumbass tried pouring into a pop/sand block in the beginning... Even after hours in an oven, I heard it and stopped before getting a volcano! POP is not investment no matter how much it looks like it. The old masters knew how to work with it, but we have this little thing called TECHNOLOGY! Don't be a dumbass or a cheap ass, buy proper investment or go find another hobby. If you read this and repeat what happened in the video, you'll get no sympathy from me.
Would using commercial investment really have prevented this? After all we have a couple of members who have done great things with PoP. Notably, none of them used a kitchen over for burnout. I know mine doesn't go up to 700+... Lucky you got enough warning to stop, the guy in the video got none. Can't imagine skipping the face shield. I recently upgraded mine to one with a hardhat attached. Need better light in my foundry to use the shaded shields effectively, but the clear one is nice. Love the spats too, they are thick and my feet and shins feel much safer than with just jeans and steel toed boots. I don't wear the chaps but I have a leather apron that covers the top of my legs. I still find ways to get little burns on myself here and there with surprising frequency. Trick is to time them so you're not pouring molten metal just then! Jeff
Yes it would have totally prevented this. Even a newbie like our rock star here could have figured this one out. I looked at a few other videos from that channel. Pretty funny stuff. He should do well on yt.
I added a leather mask to my PPE after a splash of hot metal shot up under my face sheid and burnt my chin. It's a welding mask, it had a dark glass area over the eyes that I removed. I would not be without it, once burned twice carefull. See it here
This had nothing to do with investment and everything to do with burnout. He'd have the same outcome regardless if he used commercial investment. You cannot do a burnout in a kitchen oven.
A kitchen oven is plenty hot enough to the average beginner. It was for me which obviously wasn't. You know what saved my ass was the sand mix, it started to fall apart before my eyes. This guy probably used straight PoP. If the guy would have done some research, bought proper materials, paid the bucks, there is a good chance he would have also read the instructions. I still maintain, plaster of paris from blowes isn't investment material suitable for beginners and molten metal. With all this said, I do want to pose a question... Has anyone tried 100% pop and and tried heating it to say 1500 for a couple of hours? I wonder at what point if it's actually possible to drive out the bound water or is it there to say forever like concrete? Where's @Rasper when ya need him? I know he has a lengthy burnout process often requiring DAYS to get the material ready to accept bronze.
My burn out for 40 kilos of investment is. Kiln pre heated to 200c wack in the flask for about 6-7 hrs, ramp at 85c per hour to 750c soak for 12 hours, leave kiln to cool to 450c before pouring. I can hold the flask at 450 for as long as I want within reason. I think if you are using a domestic oven it would need to be in there for quite some time to be sure all the water had been driven off.
According to Wikipedia reaching 250C is enough to drive off all water, but I guess it takes quite some time if the oven is at 250C. https://en.m.wikipedia.org/wiki/Calcium_sulfate#Hydration_and_dehydration_reactions
Some of you might find this interesting https://www.sculpturesupply.com/pdfs/techinfo/USG_Hydroperm_Process.pdf, among other things, it addresses drying a plaster based mold for metal casting. Hydroperm, btw, is a permeable plaster specifically formulated for non-investment type metal casting.
I'm pretty sure it's not, at least not the way it's normally mixed, in order to make it permeable, the instructions for hydroperm call for it to be whipped to entrain very small air bubbles into the mixture and it has additives to maintain the bubbles in the mix while it's setting up so, maybe if you whipped up PoP with a few drops of soap, that might make it permeable.