Epoxy ?

[Reddiver]

When using Epoxy as glue . Is there some rule of thumb about thickening it.. What should you use. The guy at Raka said I could use flour . I have some very very fine silica sand blast sand how about that... When I play with it I am never sure how much thickener to put in .

[Larry C]

I have used several different thickeners, mainly to control color. I mostly use fumed silica or wood flour. You can produce your own wood flour by saving the fine sanding dust from a RA sanders dust bag. I wouldn't use sand blast sand, it will just add weight. Flour should work fine as well.

Remember gluing with epoxy is different from wood glue. You don't want too much clamp pressure, just enough to hold pieces close without squeezing out the thickened epoxy. Also prewet the surfaces with unthickened epoxy before gluing. Let it soak in while your preparing your epoxy glue mix, wipe off excess and apply your thickened epoxy.

Thicken till the paste is peanut butter consistancy or untill the stir stick will stay put if you hold your cup upsidedown. There's a fine line between too thin and too thick. Experiment on scrap to get the feel for it.

Good luck,

Larry

[glassice]

If you use silica sand won't it be a pain to sand. No bonding to the sand I like talc Talc is the major component of any body filler. is a sandable filler added for fairing and smoothing the finish of fiberglass laminations. The recommended filler ratio is 2 parts talc to 1 part resin to result in a smooth, creamy semi-paste. The exact filler portion will vary by application depending on the desired consistency. Allow to stand one hour before adding hardener and using.

[Reddiver]

Thats where I have been screwing up. You are probably right about the sand blast sand hadn't thought of sanding it.. I haven't been mixing separately I have been trying to mix all three components at the same time. Where can you get Talc and will it make the epoxy really white.. I is a wood style and I would like to keep it as clear as possible

[Larry C]

If you use silica sand won't it be a pain to sand. No bonding to the sand I like talc Talc is the major component of any body filler. is a sandable filler added for fairing and smoothing the finish of fiberglass laminations. The recommended filler ratio is 2 parts talc to 1 part resin to result in a smooth, creamy semi-paste. The exact filler portion will vary by application depending on the desired consistency. Allow to stand one hour before adding hardener and using.

Glassice,
You mix a thickener into the Epoxy resin and let it sit for an hour and then add hardener? Do you know of a publication that recommends this method? I have always throughly mixed Epoxy resin with hardener and then added the thickener. Have I been doing this wrong for the last 20 years??

[glassice]

IT looks like your on the snowier coast try 1.800.838.8984 fibre glast .http://www.fibreglast.com/ By letting it set, lets resin soak in to what you are using

[Larry C]

IT looks like your on the snowier coast try 1.800.838.8984 fibre glast .http://www.fibreglast.com/ By letting it set, lets resin soak in to what you are using

You are correct, I'm on the snowy side of the country, althought most is finally gone... for now!

Glassice wrote:"By letting it set, lets resin soak in to what you are using"
Do you mean soak into the Talc?

Reddiver wrote: "When using Epoxy as glue . Is there some rule of thumb about thickening it"

From the info on Fibreglast site, the use of Talc is for making fairing putties that are easily sanded. I don't think Talc (or wheat flour) would make a strong glue. I use Wests 403 and or Cabosil for glues. I use micro balloons for fairing putties. I have not used Talc, but I may try it for fairing putties, as it is lot less expensive than micro balloons. If I do, I will try the Fibreglast method. have you used talc this way?

Please see this link from Wests Systems, a world leader on the subject.
It's a great little video. I have always thickened epoxy this way:

http://www.westsystem.com/ss/adding-fillers/

[glassice]

lets resin soak in to what you are using Talc, wood dust ,If you sand fiberglass the dust . West you pay a lot just for a name! Cabosil is a clear sand ,pain to sand

[doug hodder]

is a wood style and I would like to keep it as clear as possible

It's been my experience that anything added to the epoxy to thicken it will show that color once cured. If you want talc...check out the baby powders...some are cornstarch...others talc...and you can get it unscented...but it would smell nice when sanding. Others opinions may vary. Doug

[afreegreek]

is a wood style and I would like to keep it as clear as possible

It's been my experience that anything added to the epoxy to thicken it will show that color once cured. Others opinions may vary. Doug

that's been my experience too.. as far as I know, the only way to get thick epoxy that is clear is to let it set a while in the pot.

[Larry C]

is a wood style and I would like to keep it as clear as possible

It's been my experience that anything added to the epoxy to thicken it will show that color once cured. Others opinions may vary. Doug

that's been my experience too.. as far as I know, the only way to get thick epoxy that is clear is to let it set a while in the pot.

Actually there is a way of getting thick clear epoxy. However I dont think it would be a great glue and I think that is what Reddiver is looking for.

I think there are a couple issues here.

1) How do you mix thickeners into epoxy?, by mixing it with the resin and letting it sit for an hour before adding hardener?, or mix resin with epoxy and then add thickener?. My choice is the latter

2) What thickener makes the best glue i.e. talc, wood flour, micro fibers, fumed silica, etc. I like micro fibers and fumed silica, chopped glass, wood flour for color match.

3) Glues don't typically need sanding if you work clean. However, they need strength to hold parts together, here's where the correct thickener comes in. Different thickeners give different results in joint strength. If sanding is required for non glue situations I use micro balloons and wood flour from the same species, if possible, for color match.

3) The problem I have using clear epoxy for glue is two fold. First the joint will be weak, second the joint should not be clamped tightly like a wood glue joint. The result is a joint that is not clear, it will be darker than the surrounding wood.
This is why I prefer to match wood color with thickend epoxy and wood flour.
I use a combination Wests 403, cabosil, and wood flour in glues. With bright white 403 and small amounts of wood flour added to get exact color, it's possible to match most woods. Also tape off areas around the joint to eliminate sanding.


Ok........ I said there is a way of making clear thick epoxy. I did this once a long time ago, so I don't exactly remember the procedure. You could probably Google it.
The procedure is adding half the hardener to the resin. The mixture will set up partially and become thick but wont cure fully. I think the mixture is stored in a refrigerator, but I could be wrong about that. When a thick mixture is needed, the remaining hardener is added. You now have a thick mixture that won't run. You can also just let mixed epoxy gel and use it when it gets thick, however, you don't have as much working time.

Reddiver, these are methods that have worked for me for years building boats. Others have methods/opinions that may work the same or better.
I suggest you try mixing small amounts of epoxy and try different methods on some scrap pieces. Choose what works for you.

[Reddiver]

Thank you all things are alot more clear now

[angib]

For a glue (something which is going only in between two wood/ply pieces), microfibres (tiny strands of cotton, usually) are the important ingredient - the fibres give the glue a lot of strength and toughness (resistance to cracking). In an ideal world, I would add only microfibres but that does produce a fairly 'drippy' glue which may not be suitable for your application.

So then you want to thicken up the mix by adding silica and/or lightweight filler. Both will make the mix thicker but silica will also make it harder - this means that it will be a right pain to sand, if that is necessary. Lightweight fillers will include microbalons (tiny glass spheres), talc or wood flour and these don't add any strength but just hold the mix in place till it cures.

It's worth adding that if you add fillers until you get a fairly stiff mix, you are really using a 'filleting mix'. My favourite for that is one third microfibres, one third silica and one third lightweight filler and this produces a mix that can be used a liquid fillet weld for wood - once you've used this, you discover whole new ways of making things from wood.

Microfibres were known in my former workplace as 'scrambled egg' because that's what they look like - they may be called fibres but they look very clumpy and uneven in their dry form. Once mixed with resin, they change into something very smooth.

All fillers must, without exception, be added to epoxy that has already been mixed with hardener. If you added the filler(s) before the hardener, there is no way you will get an even mix (unless you are using a power mixer) and so you will have spots that don't cure properly.

Andrew

PS In case anyone wasn't sure, microfibres are a Yurpeen filler and when they cross the Atlantic, they magically turn into microfibers...

[Larry C]

All fillers must, without exception, be added to epoxy that has already been mixed with hardener. If you added the filler(s) before the hardener, there is no way you will get an even mix (unless you are using a power mixer) and so you will have spots that don't cure properly.

Andrew

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AMEN.........