I was told I can use talc, instead of miroballoons, in epoxy for bonding plywood to fiberglass. Will this work?

Yes, it will work. You can also use corn starch too.

Ken

Forgot to ask but what ratio 1:1:1

I dont use a specific ratio, just keep adding until it gets a "fluff-a-nutter" consistency. Microbaloons are a great thing. I also use it with CA also. Just put some on the break, and a drop of CA, and in a small puff of smoke, its strongedr than ever!

sean

Talc is stone ground to a powder cornstarch will add less weight.

Unless you are on a tight budged, try all three. I like microballons. Be sure and not breath them! You will find yourself adding them to epoxy to lighten it in lots of everyday applications too!

Ernie

As A rule of thumb always use what works.. and I will add when asking people in the know look at there master peices and then make a realistic choice..
Micro balloons : two choices Cabicille or Ammicille Both are designed as a Balloon or and epoxy holder
One adds strength other is more flexiable and can sand easier..
Use the balloons. If you would like to purchase there are people who sell Microballoons here at Rcu..
Not that expensive AnchorBond brand Is 5.00 for a Quart
Ratio as much ballons you can add till it gets to be like a Tooth paste substance..
any other questions email me..

talc is not just any stone ground up, it's a specific stone--talc stone--that has a very low density. In fact (I'd have to verify this through experimentation), I'd bet that corn starch is more dense than talc!

Talc density is 2.75. Light as far as stone is concerned but heavier than epoxy or cornstarch and much heavier than microballoons. Seems light in a container because it is a fine powder with lots of air between the particles (doesn't compress). Mixed in glue, however, most of the air is expelled and you will have no density improvement but it would likely sand better because it is a very soft mineral.

Edit:
My comments are based upon the physical properties of talc - I have not used it. It is possible that if there is enough entrained air in the mix that the overall density could be low. After all, microballoons are just small spheres full of air with a shell that is quite dense. Maybe someone has some comparative information of the relative densities of real-life mixes.

Ross

It would depend upon what you were using to measure the talc with--volume, or mass. Using volume, and talcum powder, then you'd get the same amount of entrained air that is present within the bottle.

Talc itself (as found in the stone state) may well be that dense, but we aren't talking about using talc stone, we're talking about using the ground up stuff--with all of the entrained air present. At least, that's what I get from the thread.

Cab-o-sil is not used to "thicken" resin, but to keep it from running. It's not a filler, nor intended to be. It makes your resin or glue thixotropic, that is, it won't run off a vertical surface.

Please see: http://www.eagerplastics.com/cab.htm

Not sure about "Ammicille"

For strength, though, you don't want to add a filler. If you're laminating wood-to-wood, just use a thin layer of resin. If you want to add strength, then add 1-2 oz. glass cloth between the layers. You could also use fiberglass flocking, mixed into the resin. That's basically chopped-up fiberglass cloth. The fibers are randomly oriented in the hardened mix and add a tremendous amount of strength in a lamination. Because you control how much flocking you put into the mix, you can also control the weight.

The reason I edited my post with the question about a real-life comparison is that I didn't know whether the air would remain entrained in the mixture or whether it would be displaced by the glue. I found a reference to the bulk density of powdered talc at around 800 grams/litre, depending upon mesh size (40 lb per cubic foot) and a dry bulk density for microballoons at about a fifth of that amount (8 lb per cubic foot or 160g/L). Ignoring the fact that entrained air could be different (and assuming my references are correct) the microballoon mixture should be less dense than a talc mixture. Also assumes that they can be mixed at a similar adhesive to filler ratio. You have to consider the other properties as well - strength and sandability and paintability - to determine which would be better for your application. As I mentioned, I have no direct experience with talc.

I also discovered that there are two different types of microballoons. Some are made from silica glass and others are phenolic bubbles. The phenolic material appears to have an even lower bulk density.

Found another interesting comparison on fillers:
http://www.fiberglasssupply.com/Prod...s/fillers.html

Ross