Filling cracks with powder and CA - dam building

[rtyuiop]

Hi folks,

I've been using blue tac to build little dams around any cracks/divots/holes I want to fill with metal powder and CA. The principle works, but I'm getting really fed up with the blu tac - mainly because it seems to stick to my fingers better than to timber! It also seems to harden under CA and sometimes needs to be sanded off, but it clogs sandpaper in about two seconds...

Anyone have a better technique or a better material to use for dam building?

Thanks!

Danny

[Pat]

Danny, what grade CA are you using and are you trying to fill the gaps in one go?


Try a thicker viscosity CA and take a couple of goes to fill a gap.

Roughly fill with metal + CA to about 3/4 full Allow to dry thoroughly (Overnight is best), then a light pass with metal/CA to level.

The Blue Painters tape is great for minimising the effects of any overrun. You can build walls with it!

[rtyuiop]

Ahah! Tape! Should have thought of that :). Thanks Pat.

I vary between using the technique (although I have had much better luck with thin/super thin CA than anything thicker) you describe, and more often filling a dam up above the surrounding wood and then filling with super thin CA in one go. I've been pretty happy with the results, it's just a bit of a hassle dealing with blue tac. Tape should make that easier!

[turnerted]

Danny
I have used epoxy casting resin with metal powder .You need to add the powder until it reaches a paste consistency and will not flow, then you don't need to build dams . You press it into the cavity with a small spatula ,turn off the excess when it sets ,then go over it again and fill any remaining hollows .
Ted

[rtyuiop]

I have an exceedingly checkered history with epoxy, something seems to go horribly wrong every time I touch the stuff! If I want a really big gap filled I will have to give that a try though :).

[artful bodger]

Please enlighten me.
What is CA ?

[Pat]

Cyanoacrylate = CA = Super Glue

[turnerted]

Danny
Just rememberd ,the last time I did this, I used polyester resin not epoxy . Polyester does not adhere to wood as well as epoxy, but in some applications , such as a jagged crack it will work OK and it is about half the cost of epoxy .
Ted

[dai sensei]

There is no need for dam building at all when using CA & powder. You must use thin CA, medium or thick does not work as well, you end up with more CA than the powder you want.

Best method is a little bit of thin CA first, then a little powder powder, little bit of thin CA, little bit of powder, .... until you have over filled the crack. Too much CA and you can get CA only or bubbles, just enough CA to wet it the powder, too little and you will get powder pockets that fly out. Do NOT use accelerator.

Mixing epoxy with a lot of powders generally doesn't work as you will get more epoxy than the powder you want. Epoxy does work well however if you are using pigment, powder that dissolves, or dye to colour it. Due to its viscosity however it's not to good for very small cracks.

[brendan stemp]

I have started using a hot glue gun to create the 'dam' but this is for the times I am patching up with epoxy resin.
Another way I work with CA and wood dust is to make a paste with the two on a small sheet of glass or plastic. IE place a small amount of the dust on mixing surface and then add the CA. Stir the two together to get a paste and then fill void. Work quickly, dont mix too much at once.

[rtyuiop]

Excellent advice all. I feel like this gives me a good selection of techniques next time I run into trouble!