Thread: Wood Flour verses Bote-Cote fillet & glue filler powder

The problems with wood flour is it can be a bit inconsistent in colour and fineness (it has to be really fine. It can be quite strong enough. The commercial fillers are a bit more consistent in behaviour - you kinda get to know what they will do after using them for a bit and usually they dont change their behaviour much.

Best wishes
Michael

Thanks Boatmik.
Much appreciated.

I used the boat cote filler in my first build, after first trying sawdust from a commercial sander-thicknesser's hopper. The sawdust was very fine, same as you'd get from your random orbital, but it still had a very coarse finish to it when mixed with the epoxy.

The boat cote filler was much better, easy to mix as it was always the same. It sands nicely as well. It finishes off a dark brown colour.

Originally Posted by Darce

I used the boat cote filler in my first build, after first trying sawdust from a commercial sander-thicknesser's hopper. The sawdust was very fine, same as you'd get from your random orbital, but it still had a very coarse finish to it when mixed with the epoxy.

The boat cote filler was much better, easy to mix as it was always the same. It sands nicely as well. It finishes off a dark brown colour.

Thanks Darce
Thats Music to my ears

I have just been through this. I used some fine wood dust for fillit and it seemed to be very strong but was very hard to sand. The epoxy fillers were far easier to sand - but the problem was colour. I used one that ended up being very light in colour... have just solved it by rubbing in some brown oxide (concrete colouring dust) to the sanded fillit and then clear epoxy over - looks great... in fact better than mixing it to colour the fillit as it gave a more textured finish rather than the even colour when mixing it into the thinkend epoxy to make the fillit.

Wood flour collected in a bag on your random orbital sander is fine but it tends to darken up a bit, so you need to use the product of a lighter coloured wood to the one you're filling. Just make a paste with water to test the colour match. I've sometimes used unbleached baking flour, polenta, coffee grounds (nicer smelling pox!) and even rice put through my coffee grinder to match different timbers. Anything organic seems to work great with epoxy.

I have never found a sander that produced dust to the grain size of commercially available "flour". The flour is much finer, by an order of magnitude and as a result, a smooth, creamy filler in epoxy. Dust from a sander works as a reinforcement material in epoxy, but will require considerable fairing to make smooth, which to me is unnecessary extra work.

I know a fellow that makes wood flour and sells it in our industry. It truly is ground down, just like cooking flour and then it's dried. He uses the collected dust from other wood working machines (table saw, planner, joiner, sanders, etc.) and feeds them in to the "mill".

One of the most important aspects of structural epoxy reinforcements (fillers) is the amount of overlap the fibers have. If you have larger fibers, they physically are disadvantaged to have as many "interconnections" as a smaller fiber, in the same area, so it's weaker.