Preparation - Fillers

Wood Filler

Mixing sawdust and white carpenter's glue into a stiff paste makes an excellent filler for repairing wood. It will match the existing wood surface, which is important when the finish to be applied is clear varnish. This will not work well if the wood is to be stained, because the patch will not absorb any stain.

Nonshrinking Filler

To make a strong wood filler that will not shrink and has excellent adhesion, mix sawdust and two-part epoxy glue into a stiff paste. If sawdust is not available, substitute any dry powder filler material. This filler is ideal for filling deep holes because there is no water or solvent to get trapped in the patch. The patch should be sanded within 24 hours, before the epoxy cures too hard.

Linseed Oil Putty

Linseed oil putty should not be used as a filler prior to painting. The putty dries very slowly and may bleed through the paint causing a stain. Use a commercial filler compatible with the surface and exposure.

Paintable Caulking

Paintable caulking must be allowed to dry thoroughly before it is painted. If the caulking is painted before the volatile component has evaporated, the caulking will shrink more than the paint, and the paint will crack.

Silicone Caulking

100% silicone caulking is not compatible with paint. Painting over silicone caulking will cause the paint to separate or crawl, leaving the film full of craters. Once a painted surface has been contaminated with silicone, it is very difficult to get the surface clean enough to recoat in the future. Use only latex caulking if the caulking is going to be painted over.

Paint As A Filler?....No

Paint will not fill surface imperfections such as cracks and pinholes. Although it may appear that the cracks and pinholes have been filled when the paint is wet, they appear again as the solvent evaporates and the paint drys.

Block Fillers

Block fillers should be applied to bare block only. If finish coats (especially eggshell, semigloss, and gloss alkyds) have been applied to a block wall, and there are too many pinholes, don't apply additional blockfiller at this point to try and fill them. Poor adhesion of the blockfiller will result because of the high pigment loading of the filler. Pinholes must be filled prior to the application of the first finish coat.

Latex Block Fillers

Latex block fillers are heavily pigmented latex paints. Their purpose is to fill the pinholes in concrete blocks. They rely on the surface profile of the concrete block for adhesion. Multiple coats of latex blockfillers are not recommended because of the lack of film strength at high film builds. The stress caused by the drying of topcoats (especially epoxy), can cause thick films of blockfiller to come apart, leaving blockfiller on the block and on the back of the finish coat. Block fillers are not recommended for poured concrete and will not fill the voids in concrete.