Wednesday, April 27, 2011

A Thin Gruel

The First Skull
Having popped out my first latex mold I was excited to start spitting out skulls right away. A quick trip to Home Depot for a 25-lb. bag of DAP Plaster of Paris had me ready to pour (Note: Home Depot sells the bag for $11.48; Lowe's sells the exact same bag for over $22! The only difference is the Lowe's bag comes in a box too. I don't get it).

Back in the workshop I taped up the seam of the mold and mixed up a batch of plaster. The first pour went well and after an hour and a half a came back to do the second. This is where things started to fall apart. I mixed up the plaster but was completely unable to get the right consistency. Moreover, the plaster was on some sort of speed setting because it began to set up almost immediately. I tried to add more water but it just kept getting harder and harder until I finally had to abandon that batch altogether.

A third batch also seemed too thick with a 2:1 ratio of plaster to water so I added a little more -- almost 1:1 -- and it looked an appropriate thickness, though perhaps slightly on the thin side. When I poured the mix into the skull, one area from the first pour, about a dime size in diameter, flaked off though the rest remained intact. I completed the pour though and set it aside, quite frustrated actually. I would let it cure through the night.

Cracks in the foundation
This morning I went and check on it and it had set up nicely and I was able to demold the plaster skull. There were some obvious things that stood out though. First, the skull is exceptionally thin. As you can see in the picture it is a delicate piece of fine china. And because of that it cracked along the jaw in one area when I demolded it. It otherwise looked like it was supposed to.

In checking NoahFentz's tutorial again (as must be painfully obvious by now, I do first and read afterwards), I realized he said use two cups of plaster mix to one cup of water. Oooooooh! Well that partially explains the thinness of the pour. I did one cup of plaster with the two pours (I also realize now why you're just going to be getting just 14 skulls out of one bag).

Thin as a rail
The good thing about this project is you can jump right back into it and try again. This time I mixed up the plaster according to the directions and though feeling it was a little thick I proceeded to make the pour. Well it was too thick and made moving the mix around inside the skull a challenge, but it was infinitely better coverage inside the mold so on the next batch I whip up I'll try to make it just slightly thinner so that the batter (yes, I know, Noah says it should be a pancake batter-like consistency) can flow a little more easily.

I was worried initially that because the latex mold itself was somewhat on the thin side that it would flex and crack the pour as it was setting. That may in fact be what caused that piece to flake off. But had I used the proper amounts of mix to start with it ought not to be a concern in the future.

Regardless, this was a fun project and I can see that I will indeed end up with dozens and dozens of skulls as a result.


  1. Using cold water will sometimes help to slow down the setting process, too.

  2. Shell, thanks! I think that may have been the problem with that second batch of plaster: I used warm to hot water (force of habit at that particular sink to turn on the hot water faucet since I'm always washing my hands there).

    I did the second pour for my second skull this morning and it seemed to be much better. I haven't removed the mold yet but I'm hopeful!


  3. yer killing me man...

    Yer jumping the gun...didnt expect you to move so quickly....we really didnt talk about making the plaster skull...I just showed you. If you have questions call me or email me...anytime...I promise I wont say I told you so...LOL


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