Monday, October 17, 2011

Arisu's Head Silicone Rubber Mold: Part 3 & 4

This is the last of the 4 part mold for Arisu's head and the most difficult.  It took over a week to finish.  (I did a little here and there with a few days off of course.)  I planned to make a build up of non-sulfur oil clay inside the head to the thickness of what I want the resin to cast.  The difficult part was to have both halves line up when you sculpt them separately.  This includes placement of magnets, guides (rails or tabs), and thickness.

As luck would have it, my first set of silicone molds is perfect for another idea.  I cut out a chunk of silicone from the junk molds to create a pour spout and cast hot wax in it.  I poured out the wax after a few moments to create a hollow cast of the head.  Keep in mind the mold I altered for this idea is a JUNK mold.  A MISTAKE mold.  It is NOT the mold I am trying to make to cast a prototype of Arisu's head.  I would never cut or alter an already made mold I planned to use for production.



My carving wax has a shrinkage of about 2-2.5% so it does not fit snug in the mold, but that is not a problem for what I am planning to do.  The small gap can easily filled in later with wax or sulfur-free clay.


I cut the head apart using the true head mold as a guide as to where the line should be.  This gives me 2 head parts with even thickness.  After the edges and parting lines are fixed, I removed where the eye would go.

The next part would be to figure out the mechanics of the magnets, pour hole, and vents.  I also increased the thickness by adding some sulfur-free oil clay inside the head.


The foam board is cut to create a wall around the silicone and is sealed with a low temperature glue fun to ensure the rubber doesn't leak out.  After mold release is applied, the molds are now ready for silicone rubber to be poured.


Part 3

The volume to be filled with silicone rubber is 2.5"x2.5"x1.25", which is 7.8125 cu.in.

The volume of half the head is 0.89 cu.in (with radius of 0.75").  If the clay wall in the head is 1/8" thick, the volume of the remaining half of the head is 0.52 cu.in (with radius of 0.5").

The volume for the neck is 0.1 cu.in.

The total volume of silicone rubber needed for this part of the mold is 7.81 + 0.52 - 0.1 = 8.23 cu.in.

The weight of the silicon rubber (A+B) is 6.4 oz.  This is 2.78 oz A and 3.62 oz B.

For more information about my math doing these calculations, see Part 1.


Part 4

The volume to be filled with silicone rubber is 2.5"x2.5"x0.5, which is 3.125 cu.in.

The volume of half the head is 0.89 cu.in (with radius of 0.75").  If the clay wall in the head is 1/8" thick, the volume of the remaining half of the head is 0.52 cu.in (with radius of 0.5").

The volume for the neck is 0.1 cu.in.

The total volume of silicone rubber needed for this part of the mold is 3.125 + 0.52 + 0.1 = 3.745 cu.in.

The weight of the silicone rubber (A+B) is 2.91 oz.  This is 1.27 oz A and 1.64 oz B.

For more information about my math doing these calculations, see Part 1.


Part 3 & 4

The total weight of silicone rubber (A+B) needed for Part 3 & 4 is 9.31 oz.

For measuring by volume, 7/8 cup of A+B is 9.66 oz, which is a 3.8% increase.  If I used 1 cup of A+B, that is 11.04 oz and a 18.6% increase.  Since it won't be easy measuring by volume I will be measuring by weight this time.

For a 10% increase I would need 10.24 oz of A+B.  That would be 4.45 oz of A and 5.79 oz of B.



I actually poured less than I estimated in 2 separate parts.  The first pour was to ensure a good bubble-free coating as possible on the sculpt.  I then added some scrap silicone rubber to decrease the amount of fresh silicone I would need.  The second pour was to finish filling the mold box.


The 4 part mold for the head is now done.  Next step is to cast the head in resin.  Can't wait to see how the head will look in resin.


It looks just awesome... and kinda freaky.

Part 1
Part 2
Part 1 & 2 REDO

NOTES:  I am using the Mold Making & Casting Pourable Starter Kit that I had purchased from DickBlick.com.  This kit is made by Smooth-On.  The silicone rubber that comes with the kit is OOMOO 30.  The kit comes with an instructional booklet and a DVD with video on how-to make molds and to cast.

2 comments:

  1. Oh gosh I am not really in to maths so this was a little much for me but you did a wonderful job- the best mold making 'tutorial' or series of pics I have seen.Thanks for sharing your process.

    Can't wait to see your finished product.
    I would love to follow your blog so if your interested - would love to see a followers widget.
    mwah
    Trace aka Booyagirl

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  2. LOL, yes I did post a lot of math. I could leave it out of my posts, but it is good for me to reference it in the future. I try to make it as clear as possible, but I am afraid my mind isn't very clear. :) But I do post lots of pictures.

    I will look for the follow widget and add it as soon as I can. I am happy you enjoyed my blog.

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