#materials test

[mxkitchimera]

pg7 pw6 pr122 pr 254 po73

a comparison of high chroma watercolor pigments' neutrals. PG7:phthalo green BS (daniel smith), PW6:titanium white (m graham) x PR122:quinacridone magenta (mission gold), PR254:pyrrol red (m graham), PO73:pyrrol orange (daniel smith).

Posted using PostyBirb

[ankoku-jin]

Mission Accomplished

I declare the great Mod Podge experiment to be a success! (I'm using Mod Podge matte finish; gloss may give different results.)

Here are the results:

It sinks into the pores of the polyethylene craft foam when applied in thin coats. This provides a better adhesive grip for a variety of applications and does not peel off.

However, it does not work very well as an adhesive in and of itself; craft foam Mod Podged directly to craft foam will peel apart fairly easily. Craft foam Mod Podged directly to foamcore will peel apart with a little effort.

Mod Podge sealed craft foam adheres well to paper and foamcore with other adhesives (I tried Tombow MONO dry adhesive and Elmer's glue spots.) It can be pulled apart, but it takes real effort. More than sufficient for propmaking purposes, especially if they will be fiberglassed or resin-coated.

Shell Shock brushed over coated craft foam still pulled away a bit from corners and edges. However, it worked wonderfully on paper-covered sealed craft foam. This is what I now plan to use for the upper casing on Ebony and Ivory. So it will be a four-step process before resin-coating: Mod Podge the underside of the foam, glue to prop, Mod Podge topside, glue on paper layer. But this will save me tons of modelling and sanding time.

Freeform Air is still curing. The foam can be peeled off with a bit of effort at this stage, but far less easily than with uncoated craft foam. I'll need to check it again at 24 hours, but I probably would not use it if craft foam were the only thing it was adhered to.

I extrapolate that it would be OK to use Model Magic or Creative Paperclay over a layer of paper bonded to coated craft foam, but would still recommend resin-coat or fiberglass over that for durability.

I also tried a little engraving on the resin-coated paper-over-craft foam. My Dremel was a bit big for the job, so I used this cheapo microengraver from Harbor Freight. It works beautifully. :3

[ankoku-jin]

Meta's ModPodge hack inspired me to see if I couldn't use that magic flexible polymer to address some of the issues with using craft foam. Craft foam is notoriously difficult to adhere things to, and in my last round of testing, I was able to peel the Shell Shock brushable thixotropic resin off of it (and it had a tendency to retreat from the corners and edges, leaving them inadequately coated).

So right now I've applied matte Mod Podge to some craft foam scraps to test the following matrix:

Simple adhesion: Craft foam to foamcore

Simple adhesion: Craft foam to craft foam (test flexible applications)

Surface Preparation: Resin coat applied over coated craft foam/foamcore combination

Surface Preparation: Paper layer applied over flexed coated craft foam

...i think my background in SQA is showing. ^^;; Anyway, this matrix should cover all of the applications where I planned to use craft foam. Let's see what happens! :D

[ankoku-jin]

Testing various prop finishing compounds.

#1: (Top): Crayola Model Magic

Pros: Inexpensive, easy to get, non-toxic, easy to clean up, lightweight, adheres well to foamcore, easily smoothed while soft.

Cons: slow drying, prone to cracking, does not feather out well, does not sand or machine well (tends to crumble), does not stick to craft foam AT ALL.

Notes: Cracking can be minimized by using thin layers and not trying to speed up drying time. Suitable for filling gaps, but would recommend finishing with a resin coat or fiberglass.

#2 (Middle): Smooth-On Freeform Air

Pros: Low toxicity, low shrinkage, lightweight, sandable machinable and paintable when fully cured.

Cons: Grainy and difficult to model due to softness, initially difficult to adhere to foamcore (but sticks well when cured), expensive, usually mail-order.

Notes: Working life depends on mass. Thinner mass = longer working time. Cures fully in 24 hours regardless of mass. Did not test its adhesion to craft foam, but it probably would not stick well initially.

#3 (Bottom): Smooth-On Shell Shock Brushable Urethane

Pros: Self-leveling but thick enough to fill small gaps, cures quickly (about 1 hour), low shrinkage, can be built up in coats, sandable machinable and paintable when cured, low toxicity.

Cons: Expensive, does not adhere well to craft foam (I was able to peel off partially cured resin), usually mail-order.

Notes: Can get 1/16" thick sheets of resin by pouring onto craft foam and peeling off when partially cured but still flexible. This might have interesting applications.

Waiting for Creative Paperclay to arrive so I can test that. Soon I'll also be testing Aqua-Resin, Aqua-Glass, and Aqua-Veil low-toxicity fiberglassing materials.