Hi all, I'm a serial board lurker but desperation has forced me out of the shadows! I would be really grateful for any guidance.
I've been playing with alumilite clear slow and mallee burl to make dragon eggs, bottle stoppers and pen blanks etc. Many of them turn out quite nicely, but then several months on the resin sometimes delaminates from the wood. I initially assumed this because I had sealed the wood with Modge Podge and this had prevented a good bond. So I stopped using Modge Podge and just made sure the wood was unsealed and absolutely bone dry. This had good results again initially, but again some items would delaminate. Assuming this might be due to natural movement in the wood, I've recently bought some cactus juice to stabilise the burl. The first item I made with stabilised burl was a pen blank, which initially looked good. But then I noticed this evening that the blank has delaminated. The resin does not seem to have bonded at all.
Please, if anyone can offer any advice on what I'm doing wrong, I'd really appreciate it!
You may want to try a wood sealer....the same type of sealer that would be used on a wood deck. Getting wood to completely dry out and stay dried out is tough to do if not impossible since the wood will absorb even the slightest amount of moisture and if enough moisture is absorbed , eventually it will come back to the surface.
Thanks Brian, really appreciate your input. I'll give that a try.
What confuses me is the apparent randomness of it. Some pieces are still perfect, with a seamless join between wood and resin, others have developed a slight step at the join, and others have pulled away so much that you can separate the resin from the wood with very little force.
If it is due to moisture, I'm not convinced it's moisture in the wood. I dry them slowly in the oven and weigh at intervals until they stop losing Weight. I'll generally wrap in cling film after that to avoid picking up moisture from the air until I use it. This tends to give a clean join without the typical frothing or milkiness you see when moisture is present.
Butting in... I use mallee burl frequently, and I know it is a very dense wood. Which makes it a poor candidate for stabilizing, the juice does not penetrate very far into the wood. Once you have shaped and sanded the casting, you probably have raw wood exposed.
After you have finished a piece, do you then seal the exposed wood? If you don't, the wood will continue to swell and shrink in reaction to normal temp and humidity changes. This could be what is causing your castings to separate.
I've been casting clear slow and mallee burl (and other burls) for about a year now, and I've not had a piece separate to date. I do put a topcoat on all my finished pieces.
Last Edit: Aug 12, 2020 16:31:48 GMT -5 by LawnBoy
I think you might be right there. I had thought that the cactus juice had penetrated quite well, but I am very new to stabilising. I don't put any kind of top coat on the mallee, I just sand up to 3000grit and buff to a glass finish. Thinking about it, I do wet sand at the higher grits, so this will have forced more moisture into the wood too.
Can I ask what you use/would use in this situation for a sealer?
I have used Mahoney's Walnut Oil and polyurethane successfully (there's a lot of videos of people just waxing their work, I HATE WAX). But neither of those help with that cursed ridge line that occurs when you wet sand. Currently I am coating the entire piece in a good self-leveling epoxy topcoat. This gives me a perfectly smooth surface.
Alumilite sells a good epoxy called Amazing Clear Cast. Just remember that the Clear Slow you've been using is urethane, not epoxy. The two types of resin act differently. Don't try to topcoat with Clear Slow, very thin layers always foam.
Edit: CA glue would work well if you can build it up enough to smooth over that ridgeline.
Thanks again to you both for your advice. I'm going to try a few small test pieces with some different sealers. I've already got some suitable epoxies for a start.
I've used CA on pens successfully, but the dragon eggs and bottle stoppers are just a little big for CA. Also when a ridge forms, it doesn't tend to appear until a month or more after the piece is finished.
Much appreciated Brian and Lawnboy - I'm feeling considerably more optimistic now! Cheers Chris
Well you got good advice, LawnBoy is starting to look like our resident wood expert and Brian is ours with the resin.
I can attest that the Amazing Clear Cast is a strong holding epoxy, I use it on my mold design bottoms and the thin layer on the bottom of one of my most popular designs is just starting to bend after almost a year of very rough treatment - it's a very thin layer (1/8" thick) and has to put up with some tough prying and bending and scratching so it's a testament to how strong that stuff is. And it wouldn't have started bending if the mold box hadn't started breaking and allowed the Plat to get underneath the Amazing Clear Cast which puts pressure on it when I demold.