Question on Sanding Varnish

[Dan White]

Hi. I have just stained and varnished two pieces of old furniture that I had stripped. (I didn't bother with a sanding sealer as the pieces were already quite smooth, and these aren't great pieces, anyway). I varnished once, sanded down with 400 grit, and then today put a second coat of varnish on. I am expecting that there will also be some slight roughness on this second, final coat, and so my question. Is it possible to sand this final coat with something like 600 grit (or maybe even 400 grit) without getting that white haze from the sanding? The varnish is a satin finish, so it doesn't seem to show much when I sand it. If it does still make that white haze, I thought I could take a brush with a little varnish on it and kind of dry brush the hazy area to redissolve the white parts without reintroducing enough varnish to cause another rough surface.

Any suggestions?

thanks, dwhite

[wch]

You might try, one a test piece, using Watco liquid wax and see how that works for covering any haze you might have.

I use lacquer myself more than urethane, specifically Deft wood finish in the spray cans (I don't have a compressor yet.) But I wouldn't recommend putting that over urethane.

Anyway, try the wax. Good luck.

Will

reintroducing

[Mike G]

The last shall be first. Varnish, unlike shellac and lacquer, doesn't have a solvent. Going over the area with more varnish will not redissolve the white parts. It will however, fill the sanding scratches and make them, to some extent, disappear.

With varnish and especially since you are using satin you have two choices.

Sand down a coat till it is flat and has a even scratch pattern over it. I'd suggest 220 grit rather then 400. Then apply a perfect next coat and leave it alone. .

Go through the whole rubbing out process until you reach a sheen you like.

Rubbing out is a process of cutting back the surface with ever finer grits of abrasive until the scratches disappear to the eye and the finish reaches the sheen you like.

You will probably not have to go through as many grits as you would with have to go through if you had used a gloss varnish but, then again, you won't end up with as a nice a finish as would be possible if you had used a gloss varnish.

Note; sanding sealer may make sanding the first coat easier but it can cause adhesion problems for the next coat.

[Ed G]

reintroducing

You can sand the second coat with 600 to smooth it. If you think the layer of varnish is thick enough, you can apply paste wax. The wax, in my limited experience, will even the sheen on the surface.

Please note I said "limited experience" and I'll quickly defer to those more experienced than me.

Ed

[Dan White]

OK, thanks to Will, Mike and Ed for the suggestions. I'll have to see how the second coat dried later today and decide from there. If I go with the wax idea, will it need to be reapplied in the future to cover the scratches again, or should it pretty much be good for the long term as is?

thanks, dwhite

[Mike G]

A hint. The first grit you sand with is the grit that you use to remove ALL flaws with. Every grit after that is just to remove the marks of the previous grit till they are gone.

Now, you can start out at four or six hundred grit and sand your self silly for a couple or hours or you can start with something like 220 grit, get the flaws out in an efficient and timely manner, then follow up with progressively finer grits till you get a look that gives you the warm and fuzzies.Remember the succeeding grits sole purpose is to remove the scratch marks from the previous grit. It's the initial grit that does the real work.

In the long run it is easier and faster to do it the right way. Well, maybe I shouldn't say right way. Starting with a fine grit is akin to jumping from say, 80 grit and trying to take out the 80 grit marks with 220 grit paper, but it will get you there eventually if you really want to bust your balls doing the job.

[Dan White]

I checked the pieces today, and they are dry, but still have a kind of tacky feel. It has that kind of cheap feel to it, if that makes any sense. Just for experimenting, I took some worn 400 grit to the top, and it removed what few flaws that were there. I wiped the surface with a cloth, and you can't tell I did anything and it is smoother than before I sanded it. If I try rubbing out with 220, can I go to 400 next, or are there more steps in between? I'm also a little concerned about removing all the varnish on the many turned/curved bits of molding. Any websites good at describing this method?

thanks, dwhite

[Mike G]

a touch up with 320 would be good and as for carvings and such, unless they are really really bad I leave well enough alone. It's better to take extra care in applying finish to those areas and not have to do anything further with them.

Now, if your finish is good enough to be fixed with just 400 grit without a lot of extended sanding that is fine, go for it. What grit you start and finish with depends on the quality of the application job you are working on and how much has to be taken off..

Good luck.

[Dan White]

Mike - last question and I'll leave you alone, I promise! If I go with a

220-320-400, or maybe just 320-400 is it best to do it by hand, and only in the direction of the grain? I know maybe it is blasphemy, but I have one of those orbital sanders with the square shaped sanding area. I thought that since I'm not actually sanding the wood in this step, that it might not matter for the larger surfaces.

Thanks again, dwhite

[Mike G]

Actually it isn't blasphemy. Finish doesn't have a grain only the wood does Since the aim is to reduce sanding marks to where you can't see them through the use of finer grits of abrasive there is quite a bit you can do with non grain direction work.

I frequently use a random orbit sander for initial "finishing the finish" steps.

I use a variable speed ROS at low speed. If you are using a single speed unit keep a close eye on how the finish may be building up on the sandpaper. The friction heat of the high speed from a single speed unit can cause "corning" to build rapidly on the paper and that can give you some unwanted marks in the finish.

Don't be afraid to use the ROS but be cautious and keep an eye on the paper to prevent build up.

Good luck Mike

PS I don't mind answer the questions so don't worry about asking.

[Dan White]

Thanks again, Mike. I'll get back to you when I screw something up. lol

dwhite

[pixmaker]

I agree!

I just finished a set of utility shelves (not furniture so nothing but edge-banded plywood) and shot two coats of varnish on it. Just finished sanding with a Porter Cable ROS and 320 disks.

I made a connection from the sander output port to my small shop Vac using very flexible (corrugated) one-inch bilge-pump hose (Home Depot) and a turned wooden reducer fitting to the shop Vac hose. It really helps keep the dust from building up and "melting" especially when sanding varnish. There is enough dust left to need a tack-rag wipe.

Use a light touch and you'll find it will produce a nice silky surface very quickly. (Too bad it won't get into those corners.

One final coat from the HVLP gun and it looks really good.

-- DaveinFLL ========================== It's not the heat, it's the humidity! ========================== (Think the humidity's bad? You should watch us vote!)