Mixing Fiberglass Resin & Filler Putty

  • Thread starter Migrate from As You Wish
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Migrate from As You Wish

Back in the late 40's and early 50's there was Celastic, plastic impregnated fabric that you dipped in acetone, and then laid up in strips to form an object, then in the late 50's to the present, there was fiberglass. I just realized that fiberglass has been around nearly half a century and it's still considered State of the Art! What's up with that?

I can't believe something new isn't out there yet that's quicker and easier to work with. I know there is "Plastisol" which is a hot pour vinyl you heat to 350 degrees, then slush into your mold, but I don't know if it will work in silicone. Normal urethanes seem to work, but it takes 8 - 10 shots to build up a good thickness. I've tried "Sylox" thickener in urethane, but it makes the resin brittle, and we can't have that!

I'm thinking there has to be something out there that's about as thick as say, cake batter when you pour it in, and about the consistency of polyproplyene (margarine bowls) or harder when cured.

Any thoughts form the hi-tech folks here? Thanks!

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I don't know if I am High tech but I found this stuff called Plasti-Paste in my Smooth-on catalog. They refer to it as a trowelable plastic.Here's the description: Plasti-Paste is a new self-thickening fiber resin that will hold a vertical surface without sagging. It has no odor and will cure quickly to a lightweight plastic that is impact resistant.
It looks like frosting in the picture and seems like it only takes layer to apply a nice thick coat.
Hope this helps.

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I remember reading here that someone mixed bondo with fiberglass resin to get a hard surface that sanded well. Do you add the resin to the filler putty or vice versa? And which is the proper catalyst to use, the MEKP or cream hardener? I want to do a buildup on my knee armor and want something that I don't have to worry about popping off if it flexes a little.
I just test flew this idea Monday after hearing about it for over a year. So far, it seems to work pretty good. the annoying thing with it is that you need to use both catylists.

First, measure out about 60% resin, and 40% bondo and get a rough idea how much catylist you would need for each seperately. Then mix the resin and filler till creamy, then add your drops of resin catylist, and your ribbon of filler catylist, and mix like crazy.

Good Luck!

Thanks Sarge. By the way, how were the results? Is it a harder finish than bondo? And how was the sanding?
Actually, you don't need to use the cream hardener if you don't want. It cures faster with the cream but it's not required. Bondo is just a polyester resin with a talc filler to thicken it. I use this method when a part is to be painted(because bondo creates micro-porosity that paint bonds to better), or working from silicone molds(because the talc stabilizes the resin, reducing the amount of shrinkage).
bigkidbiggertoys wrote:Thanks Sarge. By the way, how were the results? Is it a harder finish than bondo? And how was the sanding?

Ok, I just popped it out last night and it was pretty good! It might be 'slightly harder, but not that noticeable. It did have a few sticky patches, which I thought I'd be clever with and wiped straight hardener on to quick cure, but all that accomplished was to spread the stickiness over the entire helmet :(
Soo... I wiped it down with acetone, then put it in front of the heater vent for a few hours, and that took care of the worst of it. After that, I just sanded it all over with 220 and it felt ready for polishing down to 1000 grit.

I couldn't wait for feedback so this morning I jumped right into it & started filling in my knee armor. It seemed to work fine & sands just as easy as regular bondo. I'm not sure what the advantages are over regular bondo for filling work, but I could see if you are casting something you would have a nice sandable finish to start with. The only thing I found was that it doesn't cling to a vertical surface as well as regular filler putty and when it sets off, it hardens within a minute. Open time is decent though, I had about 15 minutes to work with it.
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