Monday, July 11, 2011
Epoxy thickener
I glued up a few of the chines and gunwales this weekend. Went alright. But I've been using sawdust from my sander to thicken the epoxy. I don't like the way it thickens it; not for gluing at least. I suspect the wood is 'drinking' up the epoxy and forcing me to use more than is necessary. I don't have any other 'thickener' available and wondering if anyone has any ideas or experience using other household materials to thicken epoxy? I was wondering if flour would work. No stores out here in the middle of the jungle! Thoughts? Anyone?
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Hi Geoff, if you have the option of a gas or other "clean" flame use that in preference to an actual wood fire - flying ash sticks to the "varnish" and makes it a bit rough. A quick hit with fine sandpaper would fix it though.
ReplyDeleteI've made a small sketch of my hollow ama construction, very simple, will mail it to you soon. Might try to get a small photo too.
I've not tried but it seems any fine powder can be tried as epoxy thickener: talc, flour, baking soda, pulverised limestone (sold as fertiliser), portland cement and so on. The latter two are not easy to sand! which can be useful finish on high wear areas like brushed on over the keel. Sawdust is not great, too coarse, they talk about wood "flour", ie very fine. Some use an electric coffee grinder to turn sawdust into flour for this use!
When mixing epoxy and thickener I used from 1 to 2 times thickener powder by volume to epoxy. Disposable plastic cups and-or shot glasses are great for measuring. Even cleverer is to put a cup in a cup, mark measures on outside one and re-use, pour into inside one and discard when it gets too sticky. 1 cup for epoxy, 1 for hardener, one for thickener - keep them seperate.
Pour epoxy and hardener from the cups into a ziplock bag, squeeze out excess air, zip up and mix by working with fingers. Re-open bag add thickener and mix that. Snip corner off bag and squeeze out glue! This is clean and controlled way to work with epoxy glue.
cheers Dave
PS check out Garys new design at his blog !
A couple more thoughts:
ReplyDeletethe wood will definately soak up straight epoxy. In fact it is recommended to wet wood surfaces with straight epoxy, leave for 10 mins or so to soak in, then apply thickened epoxy to glue together. If epoxy glue is applied direct to dry wood it "can" drink epoxy from the glue and give a poor join. Gluing with straight epoxy only will be even worse, if you must, try pre-wetting, wait then apply more.