SGT--Super Glue/Talcum powder
The cure for what ails ya: In the December 2000 issue of Dengeki Hobby Magazine, there was a section on scratch building a Zaku II spiked shoulder guard. The author smeared some very wet looking pinkish goop onto a half-sphere master, shaped it, and in the next photo had a sturdy hollow shell. Turns out he was using SSP-HG, which is a liquid and powder mixed together that quickly cures into a solid. This miracle filler/putty/condiment is unfortunately only available in Japan, isn't super cheap and I was between HLJ orders at the time. Based on a RAAM tip, I have been experimenting with super glue/talcum powder (SGT) to duplicate the functionality of SSP-HG.
Here are some positive observations:
1. Holy Cwap! This stuff is awesome.
2. Mixing & work time: I tried 2 different brands & viscosities of superglue (thick & thin; I did not try gel superglue), and generic talcum (Baby) powder. The resulting mix behaves the same. When mixed in roughly equal volumes, the product has a consistency of yogurt, and a wet work time on the order of a minute. The wetness and work time are a function of the glue thickness and how much talc is added; the 50/50 volume ratio works well. As it cures, or if too much talc was added, the SGT will thicken and become "gummy" or "stringy". At this point, the work time is down to 10 seconds or less. Make sure you have the application ready to go before you mix, and only mix what you need--it can't be saved. FULL cure time is about 10 minutes from mixing, and it does NOT need air contact to cure (you do not need to layer it). It does not shrink when curing, and once cured, it will not shrink at all.
3. Material Properties: Super glue by itself is very hard & brittle, prone to cracking when bent. SGT is not nearly as hard as plain superglue. In hardness, it is comparable to model styrene or cured Milliput. SGT is slightly harder than the resins I have worked with, but not significantly. SGT also seems more tolerant to flexing and bending than plain superglue. I am basing this on 2 observations. First, when cut, SGT can be shaved into thin slices. If dried superglue is shaved with a razor blade, the shaving will fracture and crumble as it peels away. SGT shaves very cleanly with the shavings curling off in one piece. The fact that SGT can curl demonstrates better bending tolerance than plain superglue. Second, I have used SGT to encapsulate the socket portion of an ABS plastic ball & socket joint. Though the SGT is very thin (tenths of a millimeter thick) in places around socket, it has not cracked or fractured in any way after multiple times assembling and flexing the joint.
4. Performance: Boy Howdy!
First, this stuff sticks like...glue. In short, it sticks incredibly well to almost anything except certain types of plastic. This includes PV, and that clear, soft plastic used to make medicine measuring cups. The little measuring cups are great for mixing SGT, and can be cleaned out by heavily flexing the cup.
Second, SGT will stick to smooth PV and ABS better than paint, but will flake off. If the PV or ABS is slightly roughed up with sand paper, the SGT will grip very well. In this picture, I applied SGT to a PV socket that I had roughed up with sandpaper and to a PV joint that was left smooth. After it had cured, there was some difficulty breaking the SGT from the smooth PV, but it came off (and actually made a nice mold of the PV hinge;). The roughed up PV is another story—the yellow arrow is pointing t where the SGT was dented from the pressure of my thumbnail to pry it off. Yes, it did come off, but I damn near broke a nail (oh my!) getting it. When I looked at the SGT contact surface for the roughed PV, it was dull. For the smooth PV the SGT contact surface was very glossy. In other words, for most practical Gundam model uses, SGT WILL bond to PV if the PV has been lightly roughed up. Has the Holy Grail of GunPla has been found!?! This allows you to slop SGT onto a PV joint, carve/sand/shape it and create a joint cover that will stay on. If anybody else can repeat this, let me know ASAP.
Third, SGT is very homogeneous (it behaves the same in any direction) when cured. This means it is GREAT for carving or sanding--much better than model styrene, which develops directional properties as it cools. I primarily use a No. 10 X-acto blade, and can shave the SGT very thinly. You can easily carve SGT to have a sharp edge, and it is tough enough to hold it. In the image to the right, the small pyramid and middle joint cover were carved from SGT. The ankle at the far right shows SGT after it has cured but before carving
5. Cost: Baby powder is dirt-cheap; unfortunately super glue in large volumes isn't. Fortunately any super glue seems to work fine, so go for the cheapest drug store bottle you can find. Note: Hobby store super glue is very expensive, and "Crazy Glue" brand is cheap. Hint, hint.
Negatives: There are several issues/downsides to SGT:
1. Very difficult to shape when applying. Imagine sculpting with sticky yogurt, and that is what you are up against. It is best to just slop it on, let it cure, then cut/sand/file to shape it. If you haven't seen how SSP-HG is used in the Japanese model magazines, they do the same--slop now, shape later.
2. Pinholes. Since SGT is mixed liquid and powder, air bubbles can/will get mixed in. When carved/sanded, some pinholes will pop out. This can partially be reduced by mixing more slowly, and fixed after the fact with putty, white out, Mr. Surfacer, whatever.
3. You cannot use SGT as cheapo resin with an RTV mold. Though SGT technically won't bond to RTV, it will grip enough to destroy the mold during removal. I haven't tried a mold release agent yet, which may help.