Mix the perfect amount of epoxy - maybe next time

[Tom Bender]

So I have a mortice that's going to take about 4 oz of epoxy, but I only get one shot at it and really don't want any squeeze out, and leave no voids. It would be great to have some sort of silly putty to make a test run. Any ideas?

[Jim Morgan]

Try sand or table salt, or something similarly dry and fine-grained, to estimate the volume you need to fill.

[Mike Henderson]

Epoxy is one thing I mix more than I need. It's not that expensive (I have a gallon of West Systems) and I don't want to run out when I'm using it. I don't mind throwing some away.

I used to do the same thing with urea formaldehyde glue that came as a powder, e.g. Weldwood. I always mixed extra because it took a fair amount of time to mix more.

Mike

[Maurice Mcmurry]

I use weight and seldom make batches as big as 4 OZ. I use grams and try to error on the lean side knowing I can mix more. I keep a mental log and notes regarding how many grams various projects take. Try making batches of 10 grams and see how many batches your joint takes. I am thinking it is a big joint?

After you glue your first joint you can weigh the leftover and spoil and know how many grams you joint required. I had a mosaic "art" project hanging around the shop that was decorated with leftover epoxy. I eventually threw it away. A neighbor took it out of our trash and has it decorating their yard.

[Scott Winners]

I have had OK luck with using blue masking tape and clear masking tape to keep squeeze out epoxy off the components at the joint edge. It is critically important, with West 105/20x anyways, to work clean and spend the first couple hours after glue up scraping off the excess, scraping off the excess. It is a time consuming pain in the neck, but it sure beats sanding an inside corner.

Hopefully you are using a thickener with that kind of volume. Have you got some sanding dust from the wood the joint is made from, like a couple tablespoons? If your joint is not enormous and you are doing a lot of gap filling, I would use some of the silica antlers. Sorry, I'll go look up the number....brb. West #406 colloidal silica. Microscopically that stuff looks like caribou antlers, a partial explanation for why it is so destructive to lung tissue.

I think I would tape off the show side of the mortise with clear packing tape, then fill it with something disposable like maybe uncooked rice, then razor knife the opening of the mortise on the show side, catch all the rice in a bucket, measure the volume of that and then subtract the volume of the tenon.

I have done four ounce glue ups with West 105/207 special clear. It is exciting, especially with all the thickener I suspect you will need, possibly even intimidating, but doable. Then main thing is to mix and mix and keep on mixing - but as soon as you are sure it is mixed start pouring so it doesn't cook off. An alternative, esp if the first mixing cup gets hot in your hand is to mix up two ounces, get it spread out on the tenon cheeks so it doesn't cook off and then mix up the other two ounces to finish.

I can't think of a material to inject into the gaps with the joint assembled to measure volume without lab equipment. A gas like Argon might work if you are fast. Epoxy is very cheap compared to shop aggravation. Have you fooled with a heat gun with regular not thickened epoxy (with an organic solvent filter on your respirator)? You might could pretreat both the mortise and tenon with heat gun excited regular epoxy to reduce soak when you do the thickened glue up. You want to heat it up to just before the epoxy starts to bubble when pre-epoxifying, and then do your glue up with the thickened epoxy at about the 24 hour mark. It is a female dog with a bad attitude, you would want to practice that on scrap, but it works good once you have the knack. The not thickened epoxy can get a good soak into bare wood, then kiss it with a heat gun at T +24 hours so the thickened epoxy gets a good bond to the previous coat. You won't have to sand between coats if you can hit that 18-24 hour window with heat.

Would love to see a picture or drawing, 4 ounces is a lot for one joint.

[Steve Eure]

I have used epoxy from this company in the past and have had great results. Granted, I have not tried this product from them, but it may be what you are looking for. ClearCote Epoxy Putty.

https://www.ebay.com/itm/352318052627

I don't know if anyone else sells it, but I did find it on ebay. You may be able to search their website if they still have one.

[Rich Engelhardt]

It would be great to have some sort of silly putty to make a test run. Any ideas?That stuff is easy enough to make if you want. So is "Play Dough".

Just google how to make the stuff.

[Ed Mitchell]

Why can't you just measure the mortise and tenon and calculate their volumes? Subtract the tenon's volume from that of the mortise. The remainder is the volume of epoxy you'll need to occupy the space.

Mix up a small bit more than needed for obvious reasons and away you go.

[Mike Henderson]

If you're doing a tenon that has shoulders, what most people do is to cut a bevel around the top of the mortise, so the excess glue has some place to go and doesn't squeeze out.

Mike

[Tom Bender]

The mortice is 1/2" wide and 40" long plus a 2" square at each end. All of it is 1/2" deep. The clearance is about 1/16" all around.

Ed, good suggestion to measure carefully to get close.

Mike, good suggestion to cut a bevel.

Rich, I'll look at making some goo.

Scott, extreme measures are probably not going to be needed

Thanks all for the advice.

[Bill Dufour]

Mix up a non newtonian fluid, pour it in push it into joint, cut bck as needed(work very fast). Then let it reliquidfy and pour it out and measure the liquid. Corn starch and water is a classic and should not effect glue.
Bill D

[Tom Bender]

Looks like the cornstarch would require some cleanup and the wood would soak up some moisture. Mercury would work better if it wasn't toxic. I happen to have some but don't think I'll use it.

[Maurice Mcmurry]

I wonder if Red Devil Zip Away removable sealant would work. The consistency is probably too thick. It is a strange and stinky product. I have a perennial client who has me caulk some drafty windows with Zip Away every fall.

Tom. How thick is the stock that the 1/2 mortis is in? I cant quite visualize it. I venture a guess at 3 pumps from West System pumps, which would be 60 grams of resin and 12 grams of fast hardner.

[Tom M King]

Mixing epoxy is kind of like ordering concrete, and buying cut length wire. If you don't get some extra to have to throw away, you're guaranteed to come up short.

[Jim Becker]

Mixing epoxy is kind of like ordering concrete, and buying cut length wire. If you don't get some extra to have to throw away, you're guaranteed to come up short.
^^ This is absolutely a "natural law" and is very much related to Murphy's Law, too... ;)

[Tom Bender]

Ok the measuring went well. I actually need 1.4 ounces plus any squeeze out and allowance for the chamfers. Yes I put tiny chamfers on the mortises. The tennons had them already.

Here's a pic of the mortise and one of the unassembled cabinet.

481558 481560

[Maurice Mcmurry]

A picture says a thousand words. I can see your concern for getting it just right. I hope you post your progress and the finished piece.

[Tom M King]

Just the bottom of that mortise probably has enough surface area to be strong enough, and some would squeeze up the sides. I would also try not to have any squeezeout.