Friday, February 13, 2015

Planning For Epoxy

The stick chair has been patiently waiting for a couple of weeks for the last bit of work before finish.  What has it been waiting for?  A German shipping company to get it's act together to deliver some epoxy I ordered.

A shipping company took more than two weeks to deliver this epoxy.  Note one of the containers is damaged, but luckily no leaks (yet).

I took some advice from The Collective, and decided the way I wanted to fix the bits of my chair that weren't quite right, is with filling the holes with epoxy.
An example of what I want to fix.
Most of the advice was to bore the end of the stick out, and insert a plug.  I decided against this, as the arm itself is not real thick, and the sticks are drilled at angles, complicating the whole thing a little.  A couple of folks suggested (like Dyami) to fill with epoxy, and Aymeric suggested the brand West Systems.

Having looked up West Systems products, I chose one that I could get here in Germany and one that was labelled as being especially clear in color.  This stuff is favored by boat builders as a finish.  If it is good enough for wooden boats, it is good enough for me.

Besides, I probably have enough now to fix about a thousand chairs!

Before I wreck my chair, though, I thought I would do a bit of practice.  We have a bamboo cutting board with a hole in it because someone in the house (I won't say who) decided to use it as a backing board when drilling a hole rather than going to the shop to get a piece of scrap.
The test piece.
The product I chose from West Systems had a recipe of 2/3 resin to 1/3 hardener.  I precisely measured this ratio out by eye-balling it.  With a small stick I dropped some into the hole and wiped the extra off with a paper towel.
Action shot.

Here is what it looked like when I left it to dry.
After an hour or so, it became clear that some of the epoxy was being 'sucked' into the wood.
After an hour of drying.
This morning, the epoxy had drawn in noticeably.
Wood suckage over night.
I think that I would rather this not happened when I try this out on my chair for real.

My plan is to use a chisel to pare a small amount of wood off of the end grain of the stick to clean it up, and drip some epoxy in the hole.

Has anyone else had this happen using epoxy?  I am wondering if the hole I am trying to fill needs pre-treating or multiple coats?  Is there a way to get this to work with just one application?  Am I doing something wrong?  Could I be misinterpreting my results?

Any feed back would be greatly appreciated.

12 comments:

  1. I have used the West system to glue ash paddles together with and various other small jobs. I have never noticed this soaking into the wood happen. I have also used it on birch ply. Bamboo is not wood, I would try a bit on some similar scrap wood if you are worried, you should be fine. Good luck, Sean

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    1. Thanks, Sean. I think I feel better now. I'll give it a go and post the results soon.

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  2. I have used literally gallons of the stuff on wooden boat restorations and other projects. Being as Gougeon Brothers (the mgf) is close by I have taken a few classes there. When you are filling gaps or holes, you can mix in some of their filler or fairing compounds to thicken the epoxy. Seeing as you have limited availability, you could mix in some sawdust of the same or like species to thicken the brew. It won't change the strength and it also will blend in better. If you are going to use it as a glue, don't use filler in those areas. One other bit of advice, on areas where there will be a bit of epoxy showing (like a hole) you should thoroughly wash and dry the cured surface as it has a tendency to form a haze (the factory call it a blush) that will throw off any attempt to finish it.

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    1. Thanks, Russ! I bought the clear stuff thinking that would probably be the least offensive to look at, but now you have me thinking. I might have to do another test.

      And thanks for the tip about finishing the cured epoxy. I wouldn't have thought to do that.

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  3. Sounds like Sean & Russ have good advice. Good luck with the patch, Brian.

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    1. Thanks Dyami. This is what is great about a woodworking blog. I love getting advice and opinions from folks who know what they are talking about!

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  4. That always happens to me when I use epoxy. The stuff seems to shrink during drying. Using sawdust as a filler looks like crap. It looks like second hand chewing gum. I prefer clear epoxy, unless reparing a knothole, then a black filler looks better. To get rid of the cavity I apply the epoxy a seond or even a third time.

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    1. Hi Kees! Thanks for the comment. I am glad to hear that a second or third application is a way to solve this. I wasn't sure that would work.

      You now have me convinced my original idea is the way to go. After all, the holes I am going to fill are pretty small in the grand scheme of things. I would hate to do something to the chair to make those spots look even uglier.

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  5. Same for me Brian, this always happened. You can use the 2-step approaches that you describe: pre-coating and then fill in, or add some more epoxy the next day. I use painter tape to "build" a tiny wall around the hole, so you can somehow overfill with epoxy. You can later remove the excess epoxy with a block plane. Another approach is - since it takes time for the epoxy to cure - to keep on filling the hole until it starts to cure. A syringe would be ideal for this kind of job, a 10 ml syringe. Also shop temp should be around 18-20°C. Hope this help! Good luck!

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    1. Good idea, Aymeric! Not having really worked with epoxy this way before I wasn't sure if this was normal or not. Building up with tape is a good idea.

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  6. I've also had this shrinking before (I've only used the 2-in-1 quickie syringes though) and just add a bit more and plane/sand flush as others have mentioned. I suspect for the hole it is an issue but for the real repair you are making, it won't be very noticeable

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    1. Thanks, Jeremy. I suspekt you ard right.

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