Great White alternate materials???

James Shaver

If ya'll remember a few months ago i did a sculpting of a Great White shark head..i did a test casting in resin and it came out malformed and misaligned..backed it with foam and its quite heavy....wondering for a wallmount to sell if maybe i should do it in urethane rubber or silicone with foam backing??? KONG came out pretty well as a urethan rubber/foam backed piece...but a little nervous to try it with a piece like this that has a bit of a "hangout/ hangover"

Did a test paintup to see how it might look...i am motivated enough to correct the defects and try remolding it as a one piece to eliminate the seams...

want to maybe get a more "professional" opinion..

Chris Ellerby

Resin should be fine for it.  My question is how did it deform?  Sometimes the weight of casting material or expanding foams can put pressure on a mold and deform it, but that can usually be solved by providing proper support with the rigid outer mold.  

Rotocasting would be a possible option to keep weight down.   You would mix up small batches of resin and rotate the mold around to build up thin layers, leaving a hollow form that can then be backfilled with foam, or even strengthened with more resin and fiberglass.

The paint job looks awesome!  

/Chris

James Shaver

Basically my keys were not big enough...i used plaster for the mother because it was supposed to be a quick test...when i slushed the resin the sleeve was slipping at the bottom and sides..i made a 2 part mold and had to "weld" the upper head and lower jaw together...due to the slippage of the upper head they didn't align properly when i went to put them together....I appreciate the love of the paintjob...that was a quick 2 minute spray LOL..

The top of the head was "sunken in" in the middle and one of the sides was concaved in..the teeth themselves did not come out as well as i wanted them to..a bit blocky instead of like the normal way a sharks tooth would look..(as i sculpted it)

I had thought maybe moving forward with making wallhangers of this shark and the dinosaurs...i might try to make an outside skin for more "realism" doing it in a ureathane rubber since they were going to be static pieces. 

Someone also gave me an idea of doing a urethane skin backed by a resin shell and filled with foam...not sure if that in itself would be a good idea ( how well would the ureathane adhere to the resin?) Made me think it was kind of a little too much work

Chris Ellerby

Ok, if the issue is the silicone inner mold separating from the outer mold there are options for that.  One option would be to spray something sticky like hairspray or a 3M adhesive into the mother mold to help give it some tack.   Nothing holds too well to silicone, but it may hold enough to help.    Another option would be to brush in some reason layers to create a skin inside the mold (and fill in the teeth) then before the resin has fully set up, and is still flexible, fill the mold with some expanding foam.  The pressure of the foam should push outward, forcing the inner mold against your outer mold.  You don't want too much pressure or the silicone can deform, just enough to keep everything in place.

Another, slightly more outside-the-box option would be to do the same resin skin step as above, then pack the mold with sand, or even dry rice, (if your mold design would allow it). Then after the skin cures, you could pour out the sand and add more layers as desired.  This would let you keep it hollow rather than the foam option, and also would allow for fiberglass backing.

I'm sure there are other good options too, those are just the first that come to mind.

/Chris