Issues with Waterlox

[Patrick Chase]

Waterlox is a phenolic based polymerized tung oil short oil varnish. Unless they are doing something massively magical - it's going to behave more or less like every other phenolic resin base polymerized tung oil short oil varnishes.. They don't burn in at all like a solvent based finish...

After having phenolic based tung oi varnishes delaminate during levelling - I am not going to go without scuffing between coats... I suppose you can do what you want...

Varnishes don't "burn in" and form a single layerless film like shellac or nitrocellulose lacquer, but they do cross-link and form chemical bonds between coats if you apply the next coat while the previous one is fairly early in its curing process. Waterlox is very slow-curing, on the order of months to full cure, which may allow it to cross-link after more than the usual ~24 hrs without sanding. I can't say I've pushed it farther than a day, though: I always do sequential coats of reactive finishes within a day of one another, and less if possible.

The key thing to recognize here is that a cross-linked bond between coats is far stronger than a mechanical bond such as is achieved by sanding. Your scuff-sanding doesn't buy you anything if you apply the next coat while the previous one is still curing, because the chemical bonds that form in that case are stronger than mechanical "interlock" anyway. Furthermore, if you allow the finish to cure before recoating then no amount of sanding can make the bond as strong as it could have been if you'd simply applied the next coat sooner. I would therefore turn your argument around and point out that you're taking the wrong action to fix the delamination issues you've had. The correct solution is to recoat sooner.

Obviously my argument doesn't hold if the sequential coats are of different finishes that don't cross-link. In that case a mechanical bond is the best you can do, and you must sand.

[Pat Barry]

Tim,

Glen is on target This looks pretty normal to me for 2 coats on walnut. I don't know what appearance you are seeking. Let each coat dry until it sands well and keep going until you get what you want. Sanding with fine, e.g. 320, grit will dull the shiny spots so that the finish looks a bit more uniform. If you want to fill the pores it may take LOTS of coats.

Doug

This has been my experience as well. Are you using the Original Sealer Finish? If it were me, I would lightly scuff sand the glossy spots, unless you are going for an overall gloss finish, in which case you need to build some more finish in the majority of the board. Those glossy spots are a bit proud of the rest of the surface, so a scuff sanding of those will bring things into a more uniform plane. I would not be concerned with adhesion if you are recoating within a few days or so.

[Thomas Hutson]

i use waterlox osf on almost all of my projects and i never sand between coats unless there are big dust nibs or bugs that land in the damn finish when its wet. or if i see a run that i missed or something. there is no need to sand between coats. for counter tops and shelves id think 5-6 coats would do great. walnut is real splotchy looking at first because of grain pattern. all its telling you is that you need more coats.