I had the Alumilite Honkin' Big Starter Kit--the one with lots of resin, but barely enough mold silicone to make a fist-sized mold? Yeah, that one. Had some greeblies that are no longer manufactured, and had a need for some for some current models (may've missed the Seeds contest, but I can still build those ships). Manned up; elected to mold and cast extras of the things I needed.
First miscalculation: not listening to the instructions of Those Who Know Better. Most things said "build yourself a container of corrugated cardboard or styrene or legos." I thought "that tupperwarish container that used to have lunchmeat in it should be perfect." Indeed, it was--until it came time to pull the first half of the two-part mold out, and I found that a tapered container is not necessarily a good thing. Still, got it loose. The special Alumilite Klay stuck to everything (two successful casts later I'm still pulling klay off of things); I learned that I don't need to pack things quite so much, as nothing even _tried_ to float to the top of the rubber.
Second miscalculation: trusting Alumilite. My bottle of silicone catalyst was less than half-full when I got it, so I ran out of catalyzer before I ran out of mold base (and I still had to cast the _top_ half of the mold). Several helpful recommendations later (and a field trip down to a store in Norfolk) and I had some Smooth-On (Moldmax 30 and Oomoo 30) samplers.
Cast the top half of the mold from MM30 (and that's stuff's _thick_). It called for an overnight cure; I actually gave it closer to 36 hours, as while it was firm, it was kind of sticky to the touch. The tapered tupperwarish container proved to be a definite drawback; the top mold leaked down the sides of the mold block (in spite of my best propping efforts). I'd slathered the top face of the mold with mold release; fortunately I'd 'cleaned' the brush by hitting the sides as well. Interestingly enough MM30 didn't stick all that well to Alumilite Sampler, so I actually didn't have to trim the halves apart with the xacto so much.
Still had to, though. Peeled a couple of places away, found where the top and bottom legitimately met, and cut along that line. Had two halves of my mold. Ugly (I learned some tricks making this mold--like steamrollering the klay flat), but appeared functional. I cleaned and picked away a lot of 'mold flash' (didn't expect that, but then, I probably didn't divide the mold halves all that well, either); fortunately, that stuff picked clean fairly well.
Took the molds to the sink. Filled the female half with water. Applied the 'squish' male half. Out came water. Poured what was left in the mold into a measuring cup. Half-ounce. Since I had to make a minimum of an ounce anyway, this wasn't a killer. Let everything dry a couple of hours.
First cast: mixed my resin. Poured resin into female half. Remembered too late to only fill all the holes about halfway (to leave room to squish). By the time I realized my mistake the resin was already hardening. I waited patiently for about ten minutes, and pulled a handful of solid resin plugs out of the gaps. A couple I may be able to use for props in the Robotech Factory; the rest just look like Earth After Disaster.
Second cast: I found, interestingly, that the hardened resin won't stick to the graduated measuring cups, so I can keep using those until I wear a hole in them. Also found that I can use a plastic drinking straw to mix the stuff. The resin actually sets up inside the straw, so the next time I use it it works even better. Hah. This time, I poured resin into each hole about halfway, and applied the squish half. Leakage, but this time I'd listened, and was doing this over a newspaper. Let the stuff sit about fifteen minutes. Pulled the halves apart. Had plenty of parts, most of which looked quite good, all joined by a thin layer/pancake of resin. Woops. Forgot to vent the squish. (Fortunately most of it broke away from the actual pieces cleanly.)
Third cast (as I needed four of one particular part) went more smoothly still, as I wasn't panicking trying to pour before the stuff hardened.
For the most part, my biggest problems (aside from the one piece that literally comes out looking melted; I really muffed the mold on that one) have just been flash (the stuff hardens up harder than styrene, so the xacto and sandpaper are getting a workout) and pinholes (which I understand is endemic to cast resin anyway; that's why I've got a tube of bondo handy). Once I got over being scared of the kit (which, technically, I was right to be. I ran out of mold ingredients before I ran out of need-to-mold, and this on a Friday evening when no place selling mold rubber was open), it was actually kind of fun.
My next couple of projects (and for this I'm likely to head back down to the Burlap store for a gallon jug of Oomoo 25) are for that stupid Big Daddy nosecone (of which I need several, thanks a LOT Estes) and two of the smaller Robotech Factory kits. I'm not likely to ever make the big leagues as a resin caster, but I'm sure happy I've gotten past the biggest hurdle (the first mold) so relatively peacefully.
Even now, the cones are on the drive units of my A27 buildup, and I'm thinking of somewhere to use the other pieces from this one.
And I just remembered that one Zoid Cannon that I wanted to add a couple of to a tank, only to find that they're not made any more. And those WOS tanks... (Woops. Getting carried away.)So far, the alumilite resin seems okay (and they do sell just that at Hobby Lobby; nobody seems to sell just the mold rubber) (ordering online is not always the best option when you were born without the Patience Gene); may or may not experiment with others as needed. Alumilite rubber cures well, but it's pricey. Smooth-On definitely gives me my money's worth. MoldMax 30 is awfully thick (although it worked this time)--like molding modeling clay, almost. The Oomoo seems runnier, which is fine with me, as that tells me it'll hit the details. (You can also get more Oomoo than MoldMax for the money, at least at the dealer in Norfolk.) I used the Alumilite mold release this time, and it'll probably last several more molds. After that I'll try some of the other suggestions listed in the Hints And Tricks section of SM.
Davey
