Grain Filling: Old School Versus "High Tech"

Extended thoughts on new and old ways to fill grain, without creating an artificial "plastic"" look. June 30, 2009

Recently I filled the grain on some walnut with several layers of Gemini precat ultralac. After several folks told me that precat can't build like that and it will crack I sanded it all down and started over.

I called my supplier and he said he had a high solids catalyzed vinyl sealer that builds well and sands great. It does both of those things, but it is giving my walnut that plasticy look that CV gives and it is freezing the figure - the figure looks fake and doesnít change with the light.

So, I am again at a loss. I haven't used enough different products to know all the ins and outs and the school of hard knocks is kicking my butt. What can I use to fill this grain that builds well but doesn't look like plastic? I have already used a paste filler - this is to finish the job.

Forum Responses
(Finishing Forum)
From contributor D:
Do you mean that you have already pastewood filled it and now youíre just asking where to go from here? If so, in my opinion you've done the right thing. From here, I would use a nitro-bar top lacquer which you can build as little or as much as you desire, putting down only one thin coat of the vinyl first and sanding. The lacquer coats should be thinned 50/50 for application and no more than two coats a day with several hours drying in between so that the solvents are well evaporated between coats. To avoid the plastic look use dye, not pigments to give it a three dimensional affect as to the chatoyancy, and do not build more than four or five coats of the nitro.

From the original questioner:
Just to clarify, I did use dye. I have never used polyurethane primer, but I have received several recommendations about it, so I will definitely check it out.

From contributor J:

What is a "high tech finish"? One that works better, faster and more durable than old school ones?

From contributor C:
Yes, I would say that what you describe is what is considered a "high tech finish". That said Ė better, faster, and more durable are over used and many times misused titles. For instance - if you come here and scratch one of my N/C lacquers or French varnish finishes, or my acrylic finishes I can have it repaired in as little as half an hour. But if I come and scratch your polyester, 2K, CV, etc - can you say the same??

From contributor V:
All said and done, these high tech, fast drying, fast everything, is taking the joy out of wood finishing. I blame the clients also to certain extent. They want things yesterday after deciding what they want today. The joy of doing it slowly and getting beautiful results is getting thrown out of the window. It's a pity that we are running without even knowing where we want to reach.

From contributor R:
Greetings all, I suppose one could call me an old-timer. Paste wood fillers have been around since air and dirt. One of the reasons that finishers frown on them is because those same finishers are in a hurry to complete the finishing job, ship it and then get paid. Paste fillers require a rather long dry time before you can start applying a solvent based finish over them.

If a finish is applied too soon the filler softens and shrinks and any other finishes applied over it softens it even more and the end results can cause an ugly grey color in the pores instead of a beautiful brown or red brown color. Itís just my opinion that to fill the grain with a clear coat robs the wood of its beauty.

Case in point - look at some of the Mahogany Duncan Phife furniture from the 30's and 40's. Now thatís a beautiful finish if you ask me. The pores of the wood have been filled with a paste wood filler, not a bunch of coating thatís been sanded down flush to the surface. Another reason for the beauty is the fact that itís been stained with a dye stain, but thatís another subject.

To use a paste wood filler, you need to thin it a bit with VM&P Naptha, you have to let it flash off until it yields a flat, dull look. You really need to press it and work it into the pores. I like a piece of burlap for this purpose. Rub it cross wise to the pores back and forth and back and forth. You canít just do a large area at a time. I like a two square foot area at a time for say a table top.

Overlap each area as you proceed and donít be tempted to renew the burlap too soon. Itís that mushy stuff thatís built up in between the fibers of the burlap that fills the pores. After going over the entire surface wipe in the direction of the grain to remove any excess filler. I donít sand any dried filler since I might sand through the color coat.

Another thing that is very important when using a filler is that the pores need to be open and free of past finishes if itís a refinish. The sealer coat you apply over a stain must be thin enough to seal in the stain but not thick enough to fill the pores. If that sealer coat is to thick in consistency, itís going to fill up some of the pores and not leave room for the paste filler. You want your pores to (if looked at under a microscope) look like a V and not a U.

The sealer coat over the dried filler should be reduced a bit so it dries fast and doesnít soften the filler. Woods like oak or ash might need a second coat of filler so thatís another reason not to spray a heavy coat.

I learned to fill the grain by following these procedures. I also learned that drying times for all finishing steps are of utmost importance to assure a durable finish in the long run. Iím never in a hurry to finish anything.