Mad Scientist Mode… Homemade Plaster Casting Stuff

Every now and then I get into mad scientist mode (insert evil laugh here).  I have officially entered Mad Scientist Mode.  It started with the Homemade Paper Clay, Homemade Glimmer Mist, the Stamp Pads, the Gesso, I have moved onto alcohol inks (I plan on trying tomorrow) and now plaster casting stuff.
I’m not sure why I operate like this but I always have.  I start something and it emerges into something else.  The gesso for example:  last night I was playing with the gesso and realized if I took a little bit (a cup or so) and added more baby powder to it, it would be like plaster.  I am not a chemist or claim to be one.  I do however know basic chemistry and have a background in Historic Preservation, so I understand how certain things work.  For example:

Gypsum plaster
Plaster of Paris is a type of building material based on calcium sulphate hemihydrate, nominally CaSO4·1/2H2O. It is created by heating gypsum to about 300°F (150 °C).[1] 
2 CaSO4·2H2O → 2 CaSO4·0.5H2O + 3 H2O (released as steam).
So what does this mean?  It means that you can achieve a casting substance with either flour or talcum (talc) powder.  They are not chemically the same but Talcum Powder or flour is close enough to achieve the desired consistency of plaster.  Many cement companies have started putting Talcum Powder in with their mixtures because it is cheaper than using lime or gypsum (wow, am I a nerd!) 
All you need for plaster is a powder (lime, gypsum, talcum powder, or flour), a binder (glue, oil, fat or crushed shells) and water.  Things like this have happening throughout history in Savannah we have a cement substance called “Tabby”.
Tabby is a building material consisting of lime, sand, water, and crushed oyster shells. It was made and used on the Sea Islands of coastal South Carolina, Georgia, and northern Florida in the Southern United States during the Colonial Period up until the early 19th century as a substitute for bricks, which were rare and expensive because of the absence of local clay. The name comes from the Spanish word, tapia, which means "mud wall".
This substance is harder than Portland Cement (one of the hardest cements on the market) and has given many City Managers headaches because you can’t drill through it, making pipe repairs next to impossible.
Experimentation is key to any new product many people start in their kitchen and with taking house hold products have made fantastic things.  I think with every new innovation we get away from the experimentation process because it has been done before and you can buy it in a store.  I however am frugal so I am constantly looking for ways to make cool art supplies cheaply.  I know my casting stuff is not perfect – it has been 8 hours and it is still curing but I think it will work for my needs. 
My recipe:
1 cup of  the Gesso Recipe
1 squeeze of baby powder
Stir it should be a thick batter consistency.  Pour into a mold.  Let set for 24 hours.
Plaster Stuff
Last night right after I poured the plaster.
Picture 17
This morning after I tried to expedite the dry with the heat gun (note the warped plastic from getting the heat gun too close).
Picture 18
The one piece I was able to get out for this blog post.  I think if I would have let it alone it would be so much smoother but I am impatience so once it is dry I will sand it instead.
To determine if a piece is still wet feel it, if it is cold to the touch it is wet, which means - leave it alone Smile
Well I hoped everyone enjoyed the nerdy side of Amanda.  I also hope this was educational and not too technical, sometimes it is hard when dealing with scientific stuff like stone and plaster make up.  If you do have questions feel free to email me or leave a comment.


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UPDATE:  I finally got the ratios figured out, check this post for the recipe.