Thanks for your help......finishing question

[Frank Ranalli]

First, I would like to thank everyone on this forum for their advice and sharing your experiences. It has been a major help to me being a VERY NOVICE DIYer. Your insight and recommendations through other threads have saved me many labor hours and $$$ and I am sure that there are many more folks on the site that can say the same.

Now a couple of questions......I have a maple dining room table that I stripped, sanded and stained. I applied a couple of coats of Minwax Polyurethane with a foam applicator while lightly sanding / scratching in between coats with 800 grit. I noticed that I was getting too many dust / particle nibs during the drying process so I switched to Wipe on Poly and applied 5 more coats with again sanding in between coats. I been waiting 4 or 5 days between these final 5 coats before sanding.

Now that I have applied my "final" wipe on coat and letting it dry for 4 days, I have noticed that I can see numerous sanding / scratching marks under this final coat. I am not sure whether these marks are down 2 or 3 coats / layers of poly but I am not sure what to do next. Obviously I want a "clear finish" in the semi gloss range but I do not know what to do to attain that look while getting rid of the sanding marks.

Since I only have a few dust nibs to be removed, I was thinking of using 1500 grit, then using a buffing compound (Mequires) and then buff polishing to finish the table. I certainly don't want to screw things up at this point so I am indebted to you guys for some tips / advise / expertise.

Again, being a novice DIYer, I look forward to your assistance and thank you again for your help.

[David Hawxhurst]

are you sure your seeing sanding marks in the poly vs the wood it self? 800 grit sanding marks are very hard to see with the naked eye. poly needs to be sanded between coats for adhesion purposes and the sanding marks disappear when you do the next layer (but anything is possible).

on a side note poly would not be a finish i would use on a table top.

[John TenEyck]

800 grit won't leave visible sanding scratches after you add the next coat of finish. So I'll bet the sanding scratches you are seeing are in the wood. If so, the only way to get rid of them is to strip off the finish and re-sand to remove them. Sorry.

John

[Frank Ranalli]

The sanding scratches are definitely not in the wood. I put 2 coats of normal poly on (with NO scratch marks) and then 5 to 6 coats of wipe on poly with sanding between coats. I looked backed at my original post and incorrectly stated of using 800 versus 320 grit. These are sanding scratches in one of the pervious wipe on poly coats.

So with that said, how can I fix this? Do I aggressively sand off a few coats of the poly and add a few more coats with lighter sanding? I am kind of looking for a solution versus what I might have done incorrectly. I am open to any ideas............thanks again.

[John TenEyck]

OK, this is just a guess, but if the scratches are in the finish I'm guessing it happened when you changed from the brush on to the wipe on poly. Maybe they are not completely compatible and the wipe on poly bridged over the scratches instead of filling them. Or it could be that the index of refraction of the two products is substantially different. Those are the only two things I can think of that might explain it. In either case, if true you'll have to sand back to the MinWax product and then build up new layers using that same product, or one compatible with it. You can make the MinWax poly into a wipe on product by thinning it with mineral spirits. 50% is the normal ratio, but it may be more or less.

John

[Frank Ranalli]

Okay John, thank you. I kind of thought I needed to sand back to a previous coat but I wanted to make sure there wasn't an easier way. I have plenty of poly on the table so it shouldn't be to tough to sand to the appropriate level. If I clean the table after sanding with mineral spirits, should I be able to see if I eliminated the sanding marks? I heard that it's possible to make sure you sanded sufficiently.

Thanks again and if you have any other suggestions, please pass them on.

[Rich Engelhardt]

Most common reason I've seen for scratches is someone not using a sanding block or using a sander instead of sanding by hand.
Buy or make a sanding block and mind you don't sand "Cross grain".

Also - liquids conform to surface irregularities, they don't "fill them". Only a mastic can do that. You can put a dozen coats on a scratched surface and the scratches will still show through.


I am kind of looking for a solution versus what I might have done incorrectlyIMHO - the solution is the elimination of something you did.
As John mentioned above, if the scratches are in the coating, you have to sand the coating down to get to them. If you continue on with the same technique that caused them, you going to just compound the problem.

Also - IMHE - 4 or 5 days between coats may allow the poly to cure too much. Just follow the directions on the can.


If I clean the table after sanding with mineral spirits, should I be able to see if I eliminated the sanding marks? I heard that it's possible to make sure you sanded sufficiently.
Yes - that's the generally accepted way of doing it. Some people (myself included) prefer to use VMP Naphtha instead of mineral spirits. It dries faster & it's less oily.

[Frank Ranalli]

Thanks Rich for your input. After thinking about what I did on previous coats of poly, I believe I did a couple of things wrong. I did in fact use a foam sanding block but I did go cross grain a couple of times plus I did it with a "loaded" piece of sand paper. Those actions are exactly were I see the sanding scratches. That occurred two layers down so I know where / how far down I have to go with my next sanding.

I will check out the VMP Naphtha in lieu of the MS........thanks again.