Filler recipe book?

I have a epoxy repair project I plan on using cabosil, milled fiberglass and microballons as fillers. But I'm unsure of the ratio's.
Iv read 1/2 teaspoon milled glass per ounce of epoxy, and no more than 1/3 as much cabosil as filler, whether it is flock or microballoons.. So I guess I will try 1/3 cabosil and 2/3 microballons. And add milled glass at 1/2 tsp per oz and test it.. But is there a filler recipe resource anywhere with general guidelines to save time or help make a order?

Thanks

 

There aren't any set ratios or mixtures, simply because they're application specific. What will the filler do, what orientation will it be placed in, what material will it be put on, what are the environmental variables, etc. are all reasons any mixture needs to be adjusted, slightly for each application.

 

Thanks PAR.

But without a basic or general starting point for a fairing compound for example.. I imagine allot of epoxy was wasted testing by inexperienced fabricators. Kind of a shame wasting all that time and materials when the information was actually recorded. Just not available..

 

The problem with fixed, even basic mixtures is they're difficult to adhere to in application. It's usually all about consistency and what it needs to do. If it's a fairly small job, a strong argument can be made for the premixed formulations, like QuikFair and T-88. These tend to be pretty costly compaired to mixing your own, but eliminates much of the guess work, lay down smooth, are consistent and predictable.

If you want to mix your own, add the "bulking agent" first, such as balloons, talc, wood flour, cotton flock, milled fibers. Mix to near the consistency you need, which will be loose, creamy or peanut butter like. Then add silica to get the viscosity you need and prevent the mix from sagging on vertical or overhead work. Getting these mixes to work every time takes some practice and you'll "smoke" a pot or two in the process, but after a while, not only will you get the "mixtures" the way you want, but you'll also be able to judge how much you need for a task.

I use a lot of the stuff, so have mixed up my own premixes. I have large plastic jars, each has a specific combination of fillers in it. I have a fairing compound mix (two types), a light structural and heavy structural mixes and a few special mixes for special applications. They all have the basic ingredients, but require some silica usually to get the viscosity I need for the application. I'll dump some in the mixing tub, add goo then get it mixed up, at which point I might add some silica, milled fibers or whatever to fine tune the mix, for the application or adjust for environmental variables.

Log onto westsystem.com and systemthree.com and download their free "user's guides" and "epoxy book", which will have a bit on mixtures, what each material tends to do to the cured goo, ratios, etc.

 

Thanks PAR. Especially the part about adding cabosil last.. But I bet I'm not the only one who would like to know what, and what ratio's, you have in your premix jars and what they are intended to do..

I will have to take another look at systems three "epoxy book".

 

Yeah, I've gotten that question before, usually from a client that sees me pouring from one of the jars. "What's 'ya got in there", to which I usually reply "magic dust". There's a part of me that wishes to covet the mixture's ratios, while another part that knows I'll be dead soon and it would be nice if some of the information I have filling the void between my ears, can be conveyed to others, so they can carry on after me. In reality, the contents are a few cups of this, a few more of that and literally pretty haphazard in nature, now. I've done it so many times I can just "wing it" and get pretty close to what I need.

Often is easier to add silica first, because it's so light and fluffy it's hard to mix in, so if the goo is really wet (neat) it's easy to "fold" it in. Of course this takes some practice, because it's easy to make a batch too stiff or dry, because you're guessing at how much you need, for the viscosity you want. It's best to "sneak up on it" with silica, to prevent this from happening. If you add the silica at the end of the process, you don't need much usually, though it is hard to mix in, you have better control of viscosity goals.

 

I do agree but I prefer to add the silica in last. Using silica first impairs the ability of the resin to wet the bulk agents, and impairs also the evacuation of the air bubbles. Silica being a thixotropic (like the tomatoe in the ketchup) more energy for mixing well will be needed if you add the silica first.
You'll discover that in fact very little silica is really needed for controlling the sagging. That'is good thing as generally the silica is the hardest and most difficult additive to sand.
A lttle trick I use when I add the silica; I do not put the silica over the mix but open a "hole" in the mix, add the silica, close the hole covering the silica and work the putty from the bottom to the surface in a circular motion.

 

Agreed with your comments Ilan and I use the same "hole" technique, folding the wet goo over it to get a good start, without it puffing out, as it's mixed. I don't use a mixing cup in the usual sense, but a large high sided tray, which is a plastic "cake carrier" I got at a local department store. I use a plastic applicator to mix, and drag the goo from one end of this 18" long tub to the other, folding it over about half way through. It helps to get the silica wet, so I'll usually wait a miniute while the coating layer has a chance to suck it up

 

by the time you make your own filler mix it is often cheaper and better to use pre-thickened epoxies. - Wet dry 700 for example is thickened with kevlar and has ground feldspar for toughness. It can even be applied underwater if necessary - about as thick as joint compound or cake icing. Think I have send a sample of it to PAR

paul oman
progressive epoxy polymers inc
epoxyproducts.com

 

Hi Paul, good to see your post. I agree for the novice user, the premixes are the way to go, if only to get consistency and convenience. On the other hand, mixing your own is a lot cheaper than the premixes, once you compare ounce to ounce costs of the materials involved. I performed some test several years ago on these premixes and resin/hardener costs were 3 - 4 times the cost of straight resin/hardener costs and the same was true of the filler materials.

Paul's "Wet/Dry 700" is tough stuff, with good elongation properties too. The ground feldspar (quartz?) does make it a little more difficult to work with (it's thick, but still spreadable), but the cured results are very satisfactory. I can see someone using this as a replacement for a kevlar tape strip down the centerline of a canoe, for example.