*
Addressed to our experts:
I know waterbase finishes have improved drastically over the last five years, I’ve seen the changes first hand. They’re easier to apply and rub-out and their appearance has improved remarkably.
I see now, that a manufacturer is touting that their product has 100% burn-in, just like nitro-lacquer. I’m no chemist, but I find this hard to believe. If this was true, that would be just another step to making these products equivalent to our beloved nitro lacquer, and maybe even better.
If this is true, is there some maximum time between quotes that a finisher must abide to??
Thanks for any input…
j
Replies
*
I know of one manufacturer who claims their product burns in 100%, just like nitrocellulose lacquer. Well, I found that hard to believe so I tried it. When I rubbed out the finish I got witness lines all over the place, which means there was very little to no burn in at all. Most products on the market today burn in to a certain degree, but it is no where near 100%. 25% would be more like it. There may be something new that I don't know about that burns in more, but I would treat a claim of 100% burn in as suspect. As for a maximum (or did you mean minimum?) time between coats, there really isn't any. You can recoat a surface as soon as the previous coat is dry to the touch. This will depend on the temperature and humidity. On a dry summer day I can recoat in 15 minutes. In the winter or on a wet day I may have to wait 30-60 minutes. If I need to apply another coat to a surface that has dried for more than 48 hours, I scuff sand it first. Hope this helps.
*Andy,Thanks for the reply.I know this isn't a forum to rip on manufacturer's, but was the name of the product you tested 'Equal' by one of the original waterbase manufacturers?? Also, what were you able to do with the witness lines that you encountered?? Were you able to eliminate them or repair the finish??My question about recoating related to the 100% burn-in feat. I just thought that if you waited too long between coats maybe you would not be able to achieve their claim of 100% burn-in, the film would be tough already. I really need to ask the manufacturer that one...thanks anyway...j
*Yes, the product was Equal. I had to sand the entire piece down and recoat it. I put on a fairly heavy coat and then rubbed it out very lightly and carefully. If a product truly burns in 100%, it shouldn't matter how long you wait between coats.
*Joe,I recently finished a cherry dining table with ML Campbell Ultrastar waterborne lacquer, and was very satisfied. I applied the finish with varing elapsed times between coats, and had no problems with witness lines. The finish was polished out with MicroMesh to a sheen just short of full gloss. I got nothing but oos and ahs. This was the first time I'd used anything other than lacquer for this kind of finish, so I was doubly pleased.Jonathan
*Jonathon,Thanks for the recommendation. Where did you purchase the Ultrastar??And did you spray or brush?? If you sprayed, any spraying problems??Most of the waterbase lacquers are a little thick, and tough to push thru my hvlp gun...j
*I've been woodworking, not at the FWW quality level, but finishing pretty satisfactorily a number of projects for years, using shellac, varnish, water based and solvent base poly, paint, oil stains and aniline dyes, etc. I've never heard of "burn in". I've just followed the instructions that came with the material. What's burn-in? Curing time between coats?
*Graeme, they are talking about the ability of subsequent coats to melt in seamlessly with earlier coats. They're calling it burn in. I know it as melt in. For instance, the nitro cellulose lacquer family contain evaporative solvents- i.e., lacquer thinner, primarily. Lacquer thinner used on its own will soften (and strip) a hard coat of pre-cat lacquer, etc.. Spray a fresh coat of pre-cat over fully cured pre-cat, and the solvent in the new coat will soften the old coat enough that the two layers intermingle and become seamless. Alchohol in shellac finishes act in a similar manner.Oil and water based varnishes on the other hand go down layer upon layer with little or no intermingling of the coats, which is why scuff sanding is needed to provide a tooth for each subsequent layer. Water based varnishes have typically needed more tooth between coats than oil based polyurethane varnish, which in my experience needs more tooth than alkyd varnish. One of the problems with this characteristic of application is the chance of rubbing through the top coat to the layer below thus revealing the join between layers; the 'witness marks' mentioned. I don't use water based varnish, but there is a technique for applying oil based varnishes 'wet on wet' that helps partially alleviate the problem, usually pretty effectively. Personally I don't rub out varnishes as people here have described unless a client really wants it, and I can usually persuade them that they don't. I prefer to apply gloss all the way through to the top coat, and put on a final coat or two of the sheen required, or cut the gloss back with some light abrasion, e.g., wire wool. Gloss varnish is tougher than any of the factory pre-dulled sheens because the dulling agent is usually finely ground silica, and this additive has a slight weakening effect on the strength of the dried film. The silica is added in varying quantities to produce the desired sheen, hence the importance of stirring any factory 'dulled' varnish thoroughly before and during application for a consistent sheen. Anyway, I'm going off on a tangent, so I'll stop there. Sliante.
This forum post is now archived. Commenting has been disabled