Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam?

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tarnyloo73

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

It's a beaut already! Really looking forward to seeing it finished.
Love the motorised articulation though I can appreciate you not intending this to be a permanent feature. Hoping the winter hangs back and allows you more work time.

Have I mentioned I'm quite envious you've made yourself a full size rex skull? :)
 

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shareahack

Active Member
RPF PREMIUM MEMBER
Thanks for following up 13doctorwho! It's been a busy summer and have only been able to get a few hours per week to work on it. It seems like I can only make significant progress if I spend full days on it.

The temperature is actually perfect right now to work outside so I'll be making more time to finish it up :D

I'm still currently in the 'obsessive detail' stage trying to match up holes and imperfections on reference material. I feel like if I've come this far I might as well put the time in and get it as close as I can. It's a bit tough working with Bondo due to the bottlenecks in mixing, work time, cure time, sculpt time. You might only get to finish a single feature in an hour if you're lucky.

x-skull-cnc-foam_3dmodel_39-bondo-detail-sculpting.jpg


Also got a nifty remote air supply feed doohickey that feeds me air from the compressor in the garage. I'm running the air through about 3 different water/oil separators and a desiccant filter to make sure the air is breathable. Even with 3M organic vapor cartridges I was still 'tasting' the fumes. I tried out the respirator yesterday and its a little air-hungry but totally worth it not breathing in Bondo for hours at a time. It plugs into standard 3M cartridge masks.

x-skull-cnc-foam_3dmodel_40-bondo-detail-sculpting.jpg


Once I've got the larger details/shapes done I'll focus on subtracting depth from the walls of the skull to give it a more fragile appearance. Nothing too crazy but something more along the lines of this actual fossil:

x-skull-cnc-foam_3dmodel_41-real-trex-fossil-skull.jpg


Also need to tackle the individual serrations on the teeth at some point. o_O

Another thing that has massively helped is this cheap/used 720 42" LCDTV that I found for $50 on Kijiji. Compared to the laptop I was using before it's been a game changer in productivity for displaying well-lit reference photos.

x-skull-cnc-foam_3dmodel_42-real-trex-fossil-skull.jpg


An interesting unexpected benefit of initially fiberglassing the foam is the ability to create awesome depth in the skull sutures by spraying a bit of acetone in the cracks and melting the foam down. There's no loss of integrity because the fiberglass shell more than rigid enough.

x-skull-cnc-foam_3dmodel_43-real-trex-fossil-skull.jpg


The next step will be coating the entire skull in polyester resin and black/brown pigments. Going to experiment with iron oxide and charcoal powder as pigments first (inexpensive powders). This will be the last protective layer before painting...the rationale being if the final paint job ever gets chipped or flaked it'll 'bleed black' underneath.

I'm choosing polyester over epoxy because I also fully anticipate it will melt some foam underneath and inside the sutures..adding more randomized textures, adding some hollowness and hopefully add to the appearance of fragility like a real fossil might have. (Let's be honest the polyester is way cheaper than epoxy :lol:)
 

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