I’ve been working on some pieces in walnut and decided to use spar varnish to finish them. I sanded to 320 and then removed the dust before varnishing. The varnish goes on nicely but the grain of the wood telegraphs through the varnish. It’s finally starting to be less of a problem after the 4th coat of varnish.
Now, a smart guy would have tried to research this first and might have tried to go through the process on a sample piece. He doesn’t live here, though. The guy who does live here was under a time crunch although the due date for the project got pushed out after he was committed to the finishing schedule.
What would you do if varnishing walnut? Would you use some sort of sanding sealer first? Or maybe seriously thin the varnish and do a coat or two with that before building the layers?
Replies
As you now know, walnut does have a rather coarse grin that will telegraph through most finishes. Like oak, some folks don't mind this and it is part of the character of the wood. However, if your objective is to have a glass smooth finish, you should have started with a grain filler. This is a past like product or thick liquid that you spread on cross grain in order to fill the pores. After dry, you sand it smooth and finish.
BTW, for interior use, spar varnish is not the best choice but, not so bad as to require a redo. At this point, after having applied several coats, if you want a smooth finish, you can sand down what you have almost to bare wood. This will leave product in the pores but, remove what is above that. Add more varnish and sand it back again. Keep doing this until the product in the pore is the same level as the surface. You will know this when the sand paper is also sanding what is in the pores. Otherwise, those spots will remain shinny. When finally sanded level, add one or two final coats. I did this on a mahogany table some years ago. It is lots of work but, it looks really good when finished.
“[Deleted]”
Thank you, bilyo. I did sand the firstcoat down to just a smooth surface before applying the second coat. I guess I figured that would take care of my problem so I was surprised by the grain still showing.
As for the choice of varnish, I was trying to use what I have on hand so I wouldn't have to buy anything new. These are plaques for some graduating high school seniors and I figured a gloss surface would be nicer than my usual favorite oil finish.
Nest time I think I'll try to get some sealer first.
Thanks again.
If you want the grain filled it would be the same process. Finish, sand, repeat, until the grain is filled and level with the surface. The only difference using something like shellac, is that it dries faster and sands easier than something like spar varnish.
Almost everything marketed as sealer is just regular finish that's diluted with the appropriate solvent. Sealer really isn't necessary except on oily woods.
Sanding sealer is milky and thick, it is easy to sand and will speed up building a finish. Since you have started coating it is unnecessary now. It will take me 5 or 6 coats of good quality spar varnish applied in thick coats and sanded down with 220 to fill the grain in mahogany or teak, walnut has about the same texture.
Sand with a stiff block to level the surface. Hand sanding or a soft block will remove material from the pores that you want to leave intact.
I recently finished a walnut desk... using two coats of Sealcoat and about 6 coats of waterborne acrylic. The two finishes (base and top coats) serve different purposes and yield different results within the sealing and finishing process.
A shellac, and Sealcoat is a shellac, darkens the grain, whereas the multiple topcoats are about as clear as you're going to get. My recommendation is to do the sealing to the point of grain coloration that you want; then, continue with top coats.
Waterborne finishes build more slowly (require additional coats per finished thickness) than oil-based finishes; however, the faster drying time and crystal-clear finish will yield a better result.
Thanks all. I sanded the varnish down with a hard sanding block and put on another coat of varnish. I had planned that all along anyway. Next time I guess I'll lay in a supply of something for sealing before varnishing.
Don't confuse sanding sealer with grain filler. They are not the same thing even though you can use multiple coats of finish, as discussed above, to fill the grain.
Yes. Sanding sealer is a product that contains zinc stearate, so the application will be easy to sand. It gets powdery. Otherwise the finish is harder, and will gum up the sandpaper. I don't like sanding sealer. I'm not confident about putting my final finish on top of it. And I think it's a solution in need of a problem.
All other sealers are just thinned down finish. It does no potential harm, but I don't think it's necessary, either. It has no place in my finishing routine.
Sanding Sealer IS a solution is search of a problem. The zinc stearate can interfere with some topcoat finishes.
For future projects you might look at a french polishing technique using pumice and shellac as a grain filler. Hard work but creates very nice results. Lot’s of yu tube stuff on this subject. The pumice acts as a sanding agent to combine wood dust as a filler. The pumice does not show when dry. Then you can use any finish to complete the project.
An approach I like is filling the wood's pores. It's not the same as grain filling. There's a good article on filling pores on Wood Magazine.com.
Best of luck,
Mikaol
How is filling the wood's pores not the same as filling the grain?
Sorry MJ, they're the same thing. My apologies.
Mikaol
So, clearly the question was about sanding sealer, but since it has digressed into a half thread about grain fillers....
For the last decade I've been doing walnut pieces in bascially one of 3 categories:
1) Multiple coats of pure tung oil
2) Shellac only
3) Shellac over oil
I recently built a box for my fathers cremated ashes and decided to do a hybrid of shellac over tung oil and the top was done with a grain filler from shellac.net: Mohawk Grain Filler, B744-1156 MEDIUM BROWN WALNUT
This was a bit scary for me because I had many many hours invested in the box already and a handpicked piece of figured walnut was band-sawed and laminated to a substrate before I started.
Lets be honest, the filler is messy and dark and scary to use. Needs a squeegee. I did 1 coat and it probably really needed 2 coats.
Long story short is that for me the final product was far smoother that I was used to but it turned out quite nice. Not sure how I feel about the filled Walnut as I'm used to seeing the grain but for the figured detail it is super ice.
Here is the final product
That looks fantastic. And a gorgeous piece of wood.
This forum post is now archived. Commenting has been disabled