Thread: Filling in wood holes/cracks: product? technique?

Minwax makes a stainable wood filler. It's not bad for small holes and cracks. I don't know if it is available in Australia.

As you mentioned "maintain strength" then epoxy is your only solution aside from butterfly keys and wood patches. It's stronger/sticks better than polyester resin, and yes, it's available in clear.

Bote-Cote Reliable Marine Epoxy
Epoxy 1000 Series High Clarity Resin 500ml Hardener 250ml | eBay
West System Epoxy Resin KIT 1 33LTR Special Clear Coating Resin KIT | eBay

photos of the slab would be good


but why do you need to maintain structural strength?

All the slab furniture I see is made from slabs as thick or thicker than the planks used to deck timber bridges -- you're not planning to use your slabs to support a B-Double truck are you?

Definitely agree that Butterfly cleats or some kind of stabilisation should be used for large cracks as no amount of resin/filler etc will add much to structural strength.

If you want an opaque finish then Builders bog turbo mixed with cement oxides works very well,I have used this combined with black oxide on timbers such as marri and jarrah that have black resin veins.
If you want a clear fill then West stytem 105 resin works ok with the 205 or clear 207 hardener.
without resorting to colloidal silica filler the west system has very low viscosity so can easily "escape" so plug or tape any escape routes.
There can also be considerable heat build-up during curing of large voids.