Epoxy mixed with sawdust still strong enough for joints??

[John C Bush]

Need to glue waterfall edge joint and fill visible voids at the same time and wasn't sure if the epoxy would lose significant strength if sawdust is added. I would like to make a paste--ish-- consistency to limit flow. This is for a beastly natural edge desk and I can only glue it up lying on its side--the desk not me--and need to keep the epoxy in place. Thanks, John.

[Doug Hepler]

John,

I have never seen data on this. I know that people use fillers with epoxy with good results. Just my opinion, I doubt that epoxy would weaken if mixed with wood flour (sanding dust). I assume that's what you meant. I think that a wood paste made of wood flour and PVA glue would be as strong or stronger, and probably less likely to run. I would prime the surfaces with unmixed PVA and then fill the voids with PVA putty.

Doug

[Mac McQuinn]

I worked with a friend building stitch & glue boats for quite a while and he always did his filleting with epoxy and wood flour in a peanut butter consistency. I never saw any issues with strength. There's a lot of stress on these joints, much more than in a piece of furniture.
Mac

[Wayne Lomman]

John, it will work best if you wet the surfaces first with straight epoxy. Adding the filler limits the amount of free resin available so this is necessary. This is correct procedure regardless of filler used. Post pics of the finished item? Cheers

[John C Bush]

Thanks for the help. John.

[Sam Blasco]

Biggest problem will be wicking in an end grain joint like that. Like Wayne said, wetting the surfaces first with neat epoxy will help -- you can even let it cure and wipe the amine blush with alcohol before bonding the actual joint. Though it is not necessary with fillers added. You can sand the joint with 400 grit to close down the avenue for wicking. Wood dust will not detract from any strength, and will actually aid in bonding. Fillers add strength to a bond. Best to add enough filler to make a catsup - mayonnaise consistency. If you're not used to working with epoxy remember to work in very small batches and don't clamp the joint with anywhere near the pressure you would use for yellow or poly adhesives, just enough to hold the joint in place and see the bead exit uniformly, otherwise you risk starving the joint of resin (epoxy fills with strength, unlike other glues) -- and hope you never have to take the joint apart! Once the epoxy sets there is no going back. There is a wealth of information or epoxy use at West Systems website.

[mike wacker]

+1 on wetting the edges with straight epoxy. Very critical step. Have had stupid good luck with "filled" epoxy, either wood flour, saw dust or West Systems Micro-bubbles. As Sam said getting your "viscosity" figured out will be key.