START HELMET – [GEMS] – ARMOR COAT –  DETAILSRESOURCES

 

GEMS

Between waiting for bondo layers and Rebound25 layers I was working on getting the gemstones correct.  They had to be translucent, red, and oval shaped.  I came to find out that a good google search term for this is “Cabochon,” which are apparently half-dome ellipsoid jewelry.  I ended up with a few different resin molds from Etsy, namely this 55mm x 40mm oval dome mold.  I had some EasyCast clear casting epoxy from a previous project from AC Moore, so I went back and picked up some mirrored foil paper and clear resin dye.  I followed these two youtube tutorials (ONE and TWO) to make a sort of half-assed test gem to get a feel for how the dyes work and such.  Things I learned:
1- Use mold release.
2- Parts A and B are NOT the same viscosity, so you can’t count on just tilting both bottles to the same angle and hoping simul-pouring will assure 1:1 ratio.
3- The dyes that look like Red / Yellow / Blue are actually Cyan / Yellow / Magenta.  To get red, 1:1 Magenta:Yellow seemed to work (did 4 drops of each, will experiment with more.)
4- Use mold release.

After some helpful assistance from Professor ClawHammer, I finally got the gem out of the mold.  It was still sort of soft on the flat side, so I guess I didn’t add enough hardener.  that’s what I get for half assing it.


I picked up a bulk set of high-intensity white LEDs from Sparkfun with the intent of lighting up the gems.  I figured that I’d be able to have the mirrored foil backing not extend to the edges of the gem, put an LED underneath and have it illuminate a ring about the edge of the gem.  If I just embedded an LED in there, the translucent nature would cause it to look like a weird glowing aberration in the otherwise smooth gem.  The LED was too focused and didn’t spread enough light sideways, so I diffused it and sanded it down, still no go.

 

I’m down to a few different experiments:
1- Still try the one where the foil doesn’t extend to the edges, only with a diffuser plate layer on the back as well.
2- Use a 2nd gem glued back to back.  It provides a lot of depth, and an LED can illuminate the “backing gem” and provide a substantial amount of illumination to the gem as a whole.  This would use a lot more resin and dye, though, and those two items are expensive.

3- I picked up a high intensity red LED and red foil backing, so far it does seem to REALLY make the gem red.  I know that sounds like a dumb statement but my conservative use of resin dye makes the gems not entirely red, the flat backs of them are almost transparent.  When the white LED is shining in, it seems brighter for sure, but you can tell that the light shining through it is white.  With the red LED you can still see the depth of the gem, but there is no doubt that it is a bright RED through and through, kind of makes it seem more like the gem itself is glowing and not just a white light shining INTO the gem.  Here’s about one billion pictures I tried to take with my cameraphone:

Picked up a small can of polyester resin from AC Moore to try gem casting with.  Financially it was a better choice, because epoxy is expensive.  In every other respect, I hated it.  The polyester resin has the same pungent odor as fiberglass resin, utilizes a bizarrely inverse catalyst system, and seems very dependent on ambient temperature.  This might have been a result of me being spoiled from epoxy being “Pour these two into a cup, mix it up, DONE,” but I will have to become more adept at using it regardless, there’s no way I’m going to cast the two or three huge gems out of epoxy.

According to the instructions and product’s website, more catalyst is used when the quantity being poured is SMALLER.  You use less or none when you are making a big pour.  I gathered that the reasoning for this was that the curing was based on heat, and a larger cast would more easily retain the heat that it is generating, whereas a smaller cast would lose its heat rapidly.  My first experiment was enough to make 2 gems, didn’t use any catalyst, left in an ambient temperature basement, approximately 60-65 degrees F, unknown humidity.  I also added a total of 8 drops of dye (4 magenta / 4 yellow).  It took near 72 hours to cure to the point where I felt comfortable removing them from the mold.  Even at the 48 hour mark they were still more gel than solid.  I didn’t know if it was the dye interfering with it or what.  In retrospect I feel as though I should have mixed it more, they advocate an extremely thorough mixing, moving it to another cup, another thorough mixing, and then pouring.


They’re still fairly tacky on the back, and putting them tacky-side down on this paper towel?  Dumb.  Don’t do that.  I understand that Tap Plastics sells a finishing spray that helps solidify the flat side of the cast, so that’ll be handy.

Made a new pour while I tried to figure out what to do here, did the thorough mix -> transfer -> thorough mix -> pour.  This one had NO catalyst and NO dye.
It didn’t really do anything fast enough (36hours or so), so I had to pour it out.  It was still very pourable.  Clearly I would need some catalyst happening in here.

Well now that I had tried the “do nothing” version of resin casting, time to try the other extreme!  I made 3 oz of resin, and after watching a plethora of resin casting videos, settled on 30 drops of catalyst (10 drops / ounce).  This 3oz was enough to make at least 4 FULL gems, but I spread it out over 5 and a half, using up all 6 cavities in the mold.  Added 16 total drops of dye just in case they turned out well, hey, I’d have 5 gems done.  I set up a little space heater aimed at it set to 75°F (The recommended temperature for the material) for a few hours, wasn’t about to leave a space heater unattended while I slept.

The next morning, I was greeted with a most peculiar result:

Those two colorless ones were the ones closest to the heater.  The two red ones on the side were the resin/dye/no catalyst/72 hr cure ones.  I’m not sure WHY the dye disappeared the way it did, HYPOTHESES:
The dye reacts adversely to heat?
The dye isn’t meant for resin?
The dye separated from the resin, floating to the top as the gems catalyzed to be evaporated off by the heater?

I’m leaning towards the first one, in looking around the internet, I find that I am not alone in this strange phenomenon – [Cosplay.com: Resin dye = fail!]
The gems, however, did cure in a record amount of time.  I want to do a few more experimental pours:
Catalyst + no heater
NO catalyst + heater
1/2 catalyst + no heater
1/2 catalyst + heater

Another thing to note is the presence of bubbles in the quick-set jobbers there.  The polyester resin AND epoxy are meant to be able to be used without the use of a vacuum chamber.  The long-cure polyester resin gems actually exhibited this:

All the bubbles sort of migrated to the center, I’m guessing this is because the resin sort of ‘climbs’ up the sides of the mold, making the back of it a slightly concave shape.
By the way, check out this insanely specialized mixing tool:

I got fed up with the smell and nebulous instructions and ordered epoxy from Tap Plastics, at this point the lack of serviceable gems is holding up production of other costume parts, so I just needed it to work.  I expended the last of my on-hand epoxy to make 2 full-cavity gems, and I’ve got enough 0.5-0.75 cavity gems to do an accurate mockup.  Now that the mold is free for a bit I’ll do those experimental resin pours.

Ran a few resin experiment pours:


Looks like for a pour that size, the 7 drops worked best.  The other two were still sort of gummy when it was all done.  The resin spray came in as well, so that took care of the tackiness, but did remove a bit of their smooth surface.  Nothing some polishing wouldn’t be able to fix up, though.  Just a heads up, plastic cups and polyester resin?  Doesn’t turn out well:

Big melty mess.

Well, time to make the big pours, let’s see how this works out

Polyester Resin, a total of 6 fluid ounces, ~20 drops of catalyst and 14 drops of dye (7 magenta / 7 yellow).  It took a while to cure, but it turned out well.  When I tried cast #2 with 30 drops of catalyst, a hypothesis was confirmed:

The heat either neutralizes or drives out the dye.  That big mostly clear gem was INCREDIBLY hot when I checked on it, I thought it was going to melt the mold it was in, so I grabbed a hammer and smashed it out of there, it was already lost.  The HOTGEM was relegated to sizing duty.  What I wanted now was a big gem with the same 4″ x 3″ footprint, but didn’t want as much depth.  Here’s what I came up with:

Plastic wrap aw yeah.  I just did my best to get it mostly taut over the cavity, it was tough because the mold is intentionally difficult to stick things to.  I FULLY expected the plastic wrap to be destroyed 0.01 seconds after pouring the resin in based on how it annihilated those plastic cups before.

Holy crap it’s (mostly) working.  I didn’t get the full 4″x3″.  In fact, I probably just got the same effect as if I had just poured it right into the mold itself.  I think I need to get the plastic wrap more taut, it really did sag in the middle more than I had anticipated.

I had to make up a light-up chamber for the fin’s gems.  Instead of making 2 separate gems, I just made one large cylinder capped by gems that would use a shared set of 2 LED’s to light up.  This was an absolute nightmare.  Working with these gems is annoying, and the only time glue seems to set properly is when whatever you’re gluing doesn’t have perfect positioning.  I made a cylinder of styrene and drilled two 3/16″ holes to put the LEDs into.  Wired those suckers up with their 33 ohm resistors annnnnd then just put it to the side for now:

 

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UPDATE APRIL 11 2012
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Ended up sort of copying what I tried to do just above, like a small light up chamber.  It was a small strip of card stock secured around the perimeter of the flat side of the gem and secured with electrical tape.

I had adhered a sheet-sized bit of the reflective red foil to a page of cardstock using spray adhesive.  I only needed one sheet for all of my small gems.  I traced the shape onto the paper side of this foil-paper bit:

I cut that out and used another strip of electrical tape to “cap” the bottom of that light-up chamber with it (foil-side in).  I used a razor to cut a cross shape into the paper where the LED would go, using a set of needle nose pliers to widen the hole:

The red LEDs are from sparkfun, they’re “super brights” and require a 33ohm resistor when using a 3V power supply (2xAA’s / 2xAAA’s).
From here they get plopped into their armor spots.