Thread: filler / bulk add for boat craft epoxy

Flour, sawdust, talc, aluminium powder, sand...

Flour as in plain flour ?

Yep. Plain or wholemeal or.....! Also dry coffee grounds, graphite powder, iron oxide(s), and sanding dust from inside the bag of your sander! Crushed granite, kitty litter, chalk dust, cement...

(not to mention the proprietary fillers)

Apparently, fragranced talc smells nice when you sand it...

Silicon carbide powder for that person you don't like who'll be sanding it himself...

On teh intarwebs, the US contingent tent to scoff at the use of non proprietary fillers in epoxy; but if they were paying what non-US people have to pay (what they pay $14 for, we pay $50 for) they might see why...

As MS said, you can use pretty much anything as a filler. I personally have used flour, wood dust/fibre and cement oxides (i.e. oxide colour additives for cement).
I also bought some phenolic microballoons (see here) that I used for some below waterline filling.

Thanks guys might use base coat (plaster compund ) got heap of it here

Colloidal silica is normally used as a thickener (such as West systems 406)

I use the Bote Cote fillers. While there is a cost, I can be sure of consistent texture and finish.
I would also have concerns about what some products might do to the strength / flexibility etc of the finished product. With the proprietary product, I don't need to be the scientist.
Cheers, Mark

Apparently, epoxy-granite mix makes a good "I can't afford a cast iron pour for my machine tool casting" alternative.

And (wheat) flour has PAR's nod of approval. Talc is good if you are looking for easy sanding.

The trick with fillers is to use the ones you need to provide the physical properties you want. Talc, for example, will make things easy to sand, though not as light as other stuff, it's cheap and readily available. Flour (yep the cooking stuff) works just as well as purchased wood flour. Sander dust usually makes a very coarse thickened mixture, so it shouldn't be used where you need to see it and it's not easy to sand, particularly compared to cooking flour. Torn up paper towels and toilet tissue works good too, but can also be harder to sand and can make for lumpy fillets. Stone dust works very well and I use it on centerboard leading edges for protection, but pray you don't have to sand it into shape, once cured. Iron fillings works fairly well, but what works much better is printer toner (iron dust and some other junk), as it's much finer and more consistent.

You can put just about anything in goo to stiffen it up. If in doubt, do a set of simple tests with a base line and several "versions" of you mixtures. Bend them, break them and remember how well they applied, then make a list of each attribute.