Sanding scratches on radiata pine

2ajsmamaAugust 28, 2009

My doors are driving me crazy! I've got 6-panel radiata pine doors, I sanded with 150 then 200, think I got everything smooth, sealed with wood conditioner, stained with gel stain. The first door I put wipe-on oilbased poly, found that I couldn't scuff between coats with 220 w/o leaving scratches I could see at low angle and strong light. So I sanded with 400, put total of 6 coats of wipe-one poly on - that door looks OK a year later, I'm sure part of it is b/c it's hung and I can't see the scratches at the angle of the light. I'm trying to cut down on the number of coats of poly I put on the other doors (that was a bathroom door).

The door I'm trying to do now, I started off the same way (150, 220, condition, stain), after staining I tried a sanding sealer coat of dewaxed shellac - followed by 320 grit hand sanding and I've got a ton of scratches and dull spots. Do I need to get out the random orbital sander? What grit? How to I handle the detail areas?

All the baseboards and casings in the house are (I believe) radiata pine, finest I've had to go with those is 220 grit, 2-3 coats of poly. I don't get why the doors are showing the scratches so much.


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Elementary question---are you sanding with the grain or across the grain?

It sounds as if you are sanding across grain---which will cuase scratches.

    Bookmark   August 28, 2009 at 4:32PM
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I'm sanding with the grain. You can only see these scratches at a low angle, when the light is coming in the window at the foot of the sawhorses and I'm crouching at the other end sighting down the length of the door. Might not even show once the door is hung, but they last one did the same thing and I went crazy with 400 grit trying to get each coat perfectly smooth. I was hoping the shellac would help this time.

The doors are radiata pine from Chile, the baseboards and trim are some kind of pine from New Zealand, is it possible the trim is something harder and sands easier?

What do you suggest for sanding/sealing/finishing the doors to get the smoothest finish (satin, not gloss, but I still like them like glass)? Thanks

    Bookmark   August 28, 2009 at 9:00PM
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I did some quick research on radiata pine as I have not worked with it---to my knowlege. Unless what I bought/used called straight grained pine is radiata.

Anyway, it has several countries/places of origin---to include California. That means there is the probability of rather wide differences in grain texture/density. Which translates into differences in sanding/finishing.

It seems the scratches are in the finish, rather than the wood. I am still learning finishing, so tips are second hand.

Spraying finish is the best way to get glass smooth coverage. Working with hand sanding requires much more than 400 grit.

It may be the best idea to get a book on finishing(library), Amazon, or large bookstore. I have one by Bob Flexner that is very good.

    Bookmark   August 29, 2009 at 9:41AM
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"The first door I put wipe-on oilbased poly, found that I couldn't scuff between coats with 220 w/o leaving scratches"

That is what the scuffing is for, you are trying to leaver very fine scratches (and remove any defects) in the finish to try and increase the bond strength of the next coat.

The final coat does not get scuffed and no scratches should show.

If you are getting major scratching you are pushing down on the paper to hard when scuffing.

    Bookmark   August 29, 2009 at 11:06AM
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I did some research too - NZ grows radiata, but as you said it may be harder than the Chilean, even though same species. I found an old forum post in Australia discussing staining radiata, and moderator recommended sanding to 320 or even 400 (I'm assuming the raw wood). Too late for that. But since the wood feels smooth, I think the scratches are just in the finish too - I was using used wt/dry sandpaper, maybe some sawdust/finish stuck on it was rougher than the paper itself, or vice versa, and I bore down too hard to compensate and sanded through the finish in spots.

I did put another coat of gel stain on today trying to smooth out the dull areas (and get the edges of the stiles and panels that I took stain off), I'll put another coat of shellac or just poly like I did the first door, then sand with 400. If that looks too dull, I'll put another coat of finish on and sand that with 600, then final coat. I've got a whole house full of doors to do, next one I'll experiment on the basement side of the basement door. I don't like to finish one side at a time (or much ahead of the other) b/c of potential for warping, not to mention taking them off, putting them up with 1 side finished, then taking down to finish the other side, but if I have to, I'll do all the insides of closet doors first til I get the technique down pat, then do all the hallway sides!

I've got to get Bob's book, some more tools too. I've been finishing and refinishing oak furniture for years, did a custom tub surround with paneled doors a few years ago (refinished the pine linen closet door at the same time but don't remember these problems - but I didn't strip and stain, just sanded and added a couple new coats of poly), ran into a little problem with staining raw oak a couple weeks ago (another post - the stain finally dried and I did 2 coats of shellac then poly on that). But I had never really worked with pine (except that one door) before 2007, when I started finishing the pine trim in our new house, and I've discovered I really hate it!

    Bookmark   August 29, 2009 at 11:14AM
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Thanks brickeye - we were posting at the same time. The problem with sanding with 220 was that I could still see some dull spots when I put the next coat on - I was bearing down too hard on the thin coat. It didn't help to use worn 220, I found 400 worked better and still got good adhesion. I thought I could do better this time with a sanding sealer, but still got uneven dullness instead of same scuff - as I said in post above, could have been clogged paper or my technique or both.

I think using finer (new) paper and just "wiping" rather than putting any pressure on is the best thing between coats. But what do you recommend to salvage this door? Think if I can't feel the scratches, the final coats of finish will even out the sheen (esp. since I'm using satin poly)? Or do I need to get it uniform first?

For the next door, what progression of grits do you recommend? I'm even thinking of starting with 100 and a palm sander to knock down all the milling marks since I can still see them in the 2 doors I've finished starting with 150. I don't have a "true" random orbital, but a B&D rectangular palm sander with "orbital action", can't fit it on panels but could use it on stiles. Then go to 150, followed by 220 with sander? Then stain, or do 320 (with sander?), even 400 (as Aussie recommended) by hand before staining?

    Bookmark   August 29, 2009 at 11:26AM
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Millwork factories are notorious for sanding with a wide-belt sander, so that all the horizontals of your door will have 100-grit cross grain scratches to be removed. But the verticals will have the same scratches, only harder to see 'cuz they are with the grain. Once they are gone, you can begin the finish sanding. I have sometimes found it necessary to use a cabinet scraper, followed by 320 paper to prep it right.

    Bookmark   August 29, 2009 at 12:00PM
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Thanks Casey - I don't have a cabinet scraper, think 100 grit *with* the grain will remove the mill marks? Then 150, 200, maybe hand sand 320 and after that anything, or just start stain? Shellac (as a sanding sealer) after stain or just start with poly?

Oh, and I think I found the one thing I hate worse than sanding pine - hanging wallpaper! Spent 3 hrs putting up a border in Ds's room today, the last foot took about 45 minutes to piece in and look decent (hidden around corner from closet).

    Bookmark   August 29, 2009 at 10:46PM
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