Filling the grain after a few coats of varnish

[Daniel Turles]

334145
Hello, first time user here, happy to finally be a part of the forum after who knows how long lurking. I have a bit of a unique dilemma that I have not been able to find additional information on anywhere. I am finishing the desk lid on a new england secretary desk that I am in the final stages of making. Initially, I put 5 coats of arm-r-seal gloss, without filling the grain, and I did not like the look. After stripping and sanding back to bare wood, I used a white timbermate filler diluted with water and dyed brown to match the mahogany board. Because the lid has a lot of string inlay, I was not able to fill the piece 100% so as not to risk dying the holly inlay. I sanded the filler, and then used a wet rag to "even" the color by blending the filler, then finally some touch up sanding over the string inlay. I have now applied 3 light coats of arm-r-seal gloss, and the grain is partially filled, definitely better than before. I will attach a photo.

Going forward, what are my best options to get a fully filled grain, without having to restrip and start from scratch? My plan was to sand with 400 grit and use some spraycan shellac for 3-5 coats, as I've read that the spraycan shellac can be good at filling the grain. After those coats, I was thinking of following up with a final coat or 2 of the arm-r-seal. What are your thoughts on this? Do you think this will be able to fully fill the grain without causing adhesion problems? The can does not mention if it is dewaxed or not. Or would it still be possible after 3 coats of the varnish to create some sort of a slurry? Thanks.

[Mel Fulks]

I've seen Durhams Rock Hard putty used in a situation like that,and it worked. It was applied with finger tips then lightly sanded off before applying more finish.

[Prashun Patel]

You can use shellac but it will take many coats. To protect your inlay, assuming it is close pored, you can seal the whole thing with shellac, then grain fill with your proper filler.

You can also just keep applying more coats of varnish, but if you are wiping arm t seal that can take a long time. Also, any varnish shrinks a little as it dries so even if you achieve a glass smooth finish, in a few days you make notice little dimples. If you are subsequently rubbing out the finish this may be acceptable. At gouge rubbing out the thinned wiped on coats of arm r seal can be problematic for other reasons.


But if you are looking for a mirror finish off the rag so to speak, I would use a good filler which will not shrink in you.

[John TenEyck]

I would keep it simply but change your strategy a little. I would keep applying Arm-R-Seal, but I would first add about 25% mineral spirits to some and apply it with a foam brush. When you do that it will flow right on, self level w/o effort and, most importantly, put on thicker layers. I would apply at least 2 coats that way right on top of what you have. Lightly sand what you have, then apply the new coats, and apply each as soon as the one below is dry enough to scuff sand w/o sticking to your sandpaper. 400 or 600 grit is fine. After those coats are on let it dry for at least 24 hours and then take your ROS sander with 600 grit and sand it flat. The pores should be filled now. If they aren't, repeat with 1 or 2 more coats. Once it's flat you can wipe on one more coat and be done, or wait a week or so and then rub out out what you have to any sheen desired.

John

[Mike Henderson]

I do like John mentioned. You put finish on and then sand it back - not all the way to bare wood, but enough to take the top layer of finish off. If you think about finish, when you spray your finish, some of it goes into the "holes" but some creates a layer on the top of the wood. If you then sand the top layer off, the finish is still in the holes.

You keep doing this until the holes fill up and you can get a mirror surface. This is called "finish fill".

One issue is that some finish will continue to shrink as it cures (or dries). If you do all this quickly, you may find that a week later you have "holes" in your surface again. What I do is get the surface to be filled, then put the project aside for a minimum of a week, then do one more sanding and finish application.

I work mostly with water borne lacquer but I assume most finishes will respond in a similar fashion.

Mike

[Oh, I sand between coats with 400 grit stearated sandpaper in my ROS, with the speed turned down. I don't know if the stearate helps but it's suppose to minimize the corns of finish that accumulate on the sandpaper.]

[Daniel Turles]

John, I took your advice and sanded the piece with 400 grit, then applied a thick coat of thinned varnish to both sides. I'm actually surprised at how smooth the brush glides and how quickly the finish is able to level when thinned. I've never thought to thin a wiping varnish since it supposedly already contains a good deal of mineral spirits but I saw a definite increase in performance, so thanks for that. I will not be able to recoat until tomorrow night, but before I recoat I will sand again with 400. Now as far as sanding goes, I can use either 400 normal or wet/dry, and I can do freehand or with a sanding block. I also have a 500 grit pad that would work on the sander. Which method of sanding would you recommend? And how much sanding do you typically do? Do you try to level the entire surface and stop only when the entire piece is uniformly dull, or do you simply try to even out the high spots?

[John TenEyck]

Glad it's working for you Daniel. I found that method of thinning Arm-R-Seal after experiencing a streaking problem when trying to wipe it on a very large surface. Arm-R-Seal has just about the same % solids as most traditional oil based varnishes at 35%. It just has a lower viscosity. So thinning it is not taking the solids content down any more than it would for another varnish, and they often are thinned to make them easier to apply.

If I just want to get rid of dust nibs I use 400 grit normal aluminum oxide paper around a rubber sanding block. If I'm trying to level the surface/get rid of pores, like you needed to do, then I use 400 or 600 stearated paper on my ROS. If you are trying to get a dead smooth surface, then I recommend you use your ROS until it's uniformly dull with no shiny low spots. Then go over it again by hand with your sand paper on a rubber or felt block. After you do that once, you shouldn't have to do it again if you apply the final coat or two so it flows out uniformly. If I want to rub out the final finish, I let it cure at least a week, two is better, then I start with 1000 grit sanding film with soapy water as a lubricant, then 1200 and 1500. From there I use an automotive polishing compound to bring it up to a gloss, but you can use micromesh products, too. I do all of it with my ROS, but some do it all by hand. I'm lazy.

In full disclosure, I have not rubbed out many finishes. I almost never use gloss, I usually spray, and I'm usually satisfied with what I get off the spray gun. But for the ones I have rubbed out, the process I described above is what I do.

John