For those of you using Epoxy????

Re: For those of you using Epoxy????

Brian from monument colorado

If you fear squeeze out in an area, you can build a "dam" out of modeling clay. Tape sometimes works. BUT clay does a better job, it fits the grain better. This is from gunsmithing's glass bedding and stock repairs. We use a 1 to 4 mixture epoxy that is a "runny" consistency. It finds places to go and oozes into cracks. Great aid in stock repair for splintered/cracked stocks.

The major gunsmithing supply company Brownells out of Iowa sells a line of epoxy under the trade name Acra. Comes in 1-4 parts, gel (1-1, like peanut butter) and various quick setting epoxies.

Somebody "splain" epoxy to me.

Bill Tindall, E.Tn.

When epoxy cures it generates heat. Wood is a good insulator. Warming epoxy lowers viscosity and it gets more "thin" than when you started.

Use liquid hide glue.

Re: For those of you using Epoxy????

Brian from monument colorado

The Acra-Gel epoxy that is mixed one to one does not appear to generate much heat while curing. And most importantly for the glass bed operation in gunsmithing it tends to stay where it is put and oozes only under pressure. The 4 to 1 "runny" Acra-glas epoxy definitely generates heat. Epoxy is real good at filling gaps. It can also be colored. If gap filling is not a requirement ordinary glues could be used instead. One thing to keep in mind is that epoxy is not very good under shock conditions

Re: Somebody "splain" epoxy to me.

Larry Clinton At Frankfort, (Central) Indiana

Bill I have used many 5 gallon buckets of epoxy as an Engineer prior to my retirement. The epoxy actually does thin when heat is applied prior to mixing.

But if the heat is generated by the reaction with the curing agent it is to all appearances a static condition as the "curing" speeds up with heat. So although the more heat generated in theory should result in thinning the faster curing results in thickening.

I have used several different types of epoxies - actually some are single component heat cured.

Re: Somebody "splain" epoxy to me.

john lucas

System 3 Mirror coat will run through Red Oak pores as it cures. It's the only epoxy I have had do that. It gets extremely thin as it heats up to cure. I don't know if standard System 3 does that. I was drilling holes in scraps of wood and filling them with epoxy so that I could turn it later. I picked one up and there wasn't any epoxy in it. I could not figure out what happened until I looked at the bottom and realized that it had actually run through the pores of the Red Oak blank that I had picked up.

Interesting....

Barry Irby

I had not thought of the epoxy thinning as it set. It appeared to be getting thicker in the cup as I used it. Did not occur to me it might thin out in the joint.

This is white oak. Not the red oak John mentioned, but has some defects in if like tiny bug holes. They may account for few of the leaks. Some of the joints may not have been as perfectly tight as I thought. Some of the shoulders had spaces way less that the thick of a piece of paper. I thought the epoxy would fill these gaps, but it may have leaked out. Interesting to me that I cleaned up twice on the latter three chairs and yet there were still a run or two. I may have missed them, but I think they occurred later.

I did not think of hide glue. Might have been a good idea.

The good news is the chairs are cleaned up and appear rock solid.

On to sculpting the seats. Thanks for the help.

Epoxy help

Keith Newton

Hey Barry, You need to get some colloidal silica to thicken your epoxy with. It is a very fine / light weight powder that can be added to achieve any viscosity you desire. Since your epoxy can stay liquid for a couple of hours before it kicks, depending on the temperature, it can sag or run. By mixing silica in, you can make it any thickness you wish from latex paint, catsup, mayo, or peanut butter. For a tight joint you might want somewhere in the middle because the thicker might make it hard to assemble.

Thanks Keith

Barry Irby

That's what i was looking for. On later pieces I used some very fine saw dust and it seems to help, but not much.

I am going top fume these chairs. (they are white oak) Now that I think of it I wish I had died the epoxy dark brown or used some walnut sawdust in it, just in case some of it shows, it wouldn't stand out after the fuming.

Does adding the silica or sawdust or dye weaken the bond?

Additives in epoxy

Keith Newton

You can mix almost any dry powder to epoxy, but that may not prevent it from sagging on a vertical surface. Imagine painting a wall with honey. You know it isn't going to dry, so it is going to sag. Would mixing sawdust in to make it thicker prevent that? I don't think so.

As for color, I will sometimes mix a bit of sander dust in with the epoxy silica mix to darken the color. It doesn't take much dust to do it, whereas just going with straight walnut dust will end up much darker than you would expect, and still might sag.

Back probably 20 years ago when I was ordering epoxy in pail quantities I would sometimes forget to order silica because didn't check how much was in the oatmeal size cardboard tube container. Finally while placing an order I ask what was the next size up from what I'd been getting. The rep on the other end of the line said 10#, so without a thought I said OK without even asking the price. It came in a big bundle large enough to fill a garbage can like you spy out on the curb. I'm sure I will never use it all, so if you want to make another trade, make me an offer.

Re: Somebody "splain" epoxy to me.

Keith Newton

Larry, I agree. The amount of heat generated is relative to the depth of the epoxy in the container. If it is spread thin as in a glue joint, I'm not sure you could feel the heat generated, and once I can feel the heat in the container, it is too late to continue spreading that mix or batch.

Re: Thanks Keith

William Duffield

Colloidal silica actually strengthens the bond. So do fine wood dust particles, but not as much. Dye (I've only used TransTint) will weaken the bond somewhat. Warning: If you add the dye before you have thoroughly mixed the resin and hardener, it can drastically weaken the bond, and even keep it from hardening. DAMHIKT!

Note that sapwood white oak vessels are also open from end to end. The tyloses do not close up until the oak tree converts the sapwood to heartwood.

https://en.wikipedia.org/wiki/Tylose

I have had the epoxy squeeze out the pores on the end of the stile when assembling a stile and rail loose tenon joint with dominoes and an open grain wood.

Re: Thanks Keith

Brian from monument colorado

An alternative is to try AcraGel, it is a thicker formulae. Doesn't tend to flow. It stays where it is put. It is thick by design not by observed chemistry.