Grain Filler Choices
Advice for a finisher who wants a full grain fill and a tough, but repairable, top coat. July 3, 2008
Question
I have been having my work finished professionally and we are using polyester to fill the grain and topcoating with conversion varnish. The finish looks great but is difficult to repair when damaged and makes for a brittle shell over the furniture. What other options are there for filling the grain (to still have the full fill effect) that will not discolor the wood or leave traces of filler visible in the pores - something that can be topcoated with something like lacquer so the finish is not so thick and brittle? The polyester/conversion varnish is quite expensive when applied professionally and I am hoping to find something I can use in my shop to do the fill work before sending the work out for final topcoating.
I should point out that I have read all of the archived info in the forum about grain fillers, etc. and am just looking to see if there is something new, maybe in waterbase fillers, that dries clear and doesn't add color like traditional grain fillers. Most of my work combines multiple wood colors. I know polyester is a great product for filling but it is expensive and the final finish is much more difficult to repair than a thinner lacquer finish. Not every client is ready for the high finishing cost and a different alternative full fill finish would help sell some jobs.
Forum Responses
(Finishing Forum)
From contributor A:
I can't speak for the waterbase fillers but when I want to do a fill on walnut or mahogany or oak, etc. I use shellac and 4F pumice. Although this looks grey in the pores when by itself, it clears up when overcoated with solvent finishes such as lacquer, polyurethanes, and even polyesters. Make a batch that is pretty stiff but easily brushable and apply then use a credit card or other to squeegee the excess off. Let dry overnight then sand with whatever you plan on being your last grit but use black silicone carbide paper to do so - it cuts any excess off quicker though others will work if you don't have it. Try a decent size sample and have your finisher coat it out and see how you like it. Use any finish you desire depending on the durability and all else needed.
From contributor B:
What wood species are we talking about? You also say "furniture" - can you be a little more specific? Maple or cherry doesn't need to be grain filled, so that could be an option. Also polyester topped with CV doesn't seem like a great idea to me. I think you could have an adhesion problem potentially. I would prefer a 2k urethane topcoat myself.
From the original questioner:
I will try the shellac and pumice mix. I have done something similar with plaster of paris on some very white veneer in the past. I don't remember what I mixed it with though. I am not looking at any specific project for this but rather most of my work so the materials can be anything from Ash to Wenge and everything in between. Every piece is different. I have been using the polyester with conversion varnish combo for a few years and haven't seen any trouble yet, but maybe it is still too soon.
From contributor D:
I don't understand why the finish is "thick and brittle." The polyester sealer should be sanded back aggressively to level it out and eliminate dimples in the surface where the pores are. That only leaves a thin film over the wood. Then a coat (or two) of CV should not add a very thick film and it should be very tough.
If you want a lacquer finish, then why not use a natural/clear paste wood pore filler and lacquer? If your finisher doesn't offer that option, can you find another who does? What type of work are you doing?
From contributor A:
If you're going with that then use Zinsser sealcoat for the shellac part to test with to insure there are no adhesion concerns from wax like the others have.
From the original questioner:
The finish is brittle in the sense that when a dent occurs the finish fractures as the wood is dented making for a difficult and usually noticeable repair, unlike a lacquer finish unless built heavily.We are not using polyester sealer but polyester finish applied heavily and essentially ground flat while filling the grain. For gloss finishes the polyester is flattened and buffed with no other topcoat.
From contributor B:
Is it possible where the dents are the CV is lifting? Polyester doesn't usually fracture when dented. Do the gloss finishes do the same thing?
From the original questioner:
I have been lucky enough to not dent a gloss finish yet. I can't tell if it is just the CV lifting or if the CV and polyester are fracturing together. That would be my guess but it would just be a guess. Either way the end result is the same, damage needing repair, thus the attempt to switch to a finish that will be easier to repair and less prone to hard damage.
From contributor A:
If you're looking for easy repair stay with evaporative finishes - lacquer, acrylic, etc. but if you need excellent water and household chemical resistance I would go with Contributor B's suggestion as a 2 pk urethane. I've used direct gloss systems for 24 years with both cat varnishes and 2 pks with no severe problems like you are mentioning. I also know they are sometimes very difficult to repair, but for me they were a selling point that I used up front - telling my clients if for some reason they did get damaged I would only have to strip off the cat or 2 pk and re-sand, fix damages, and recoat/polish. I only ever had to do that once in a hurricane situation where the roof caved in on a piano. Duratec and Seagraves were my direct gloss systems for the most part.
From contributor E:
To contributor A: What do you use to strip 2k? I always thought you sand that stuff off.
From contributor A:
I normally use a non-wax remover based on methylene chloride and methanol with methyl cellulose to thicken it with into a gel type of condition. I put it on, cover the surface with polyethylene, and let set for an hour or more then carefully scrape it off. It usually takes 2 or 3 coats to do, or usually just one with conversion varnish. Then I use other solvents to wash any remaining left over areas off - sand 220 and ready it for re-coating after I do the repairs and spot spray over them.
From contributor F:
As a professional furniture finisher I can advise you to use sanding sealer based on cellulose lacquer as the first coat after staining, then use clear lacquer( Cellulose base) and when it becomes dry, spray a thick layer of NC sanding sealer again and let it to dry perfectly for 36 hours. Then sand it carefully with 180 or 220 sand paper and apply topcoat.
