Sanding wood question?

Question

Ok, I am refurbishing my house, I have stripped paint from all wooden surfaces (window sills, door frames, staircase etc).
After that I have sanded all the wood with very rough sandpaper. The surfaces are smooth to the touch. I am planning to varnish them with clear matt varnish.
Do I need to sand everything again with a medium or fine sand paper before that or can I just wash it, let it dry and then varnish? Does it have to be treated with something before being varnished?
Is there any trick to do with soft wood to make it stronger when varnished? (I've heard of Ronseal "diamond-hard" varnish - is it any good?)

Thanks for your help

bstuck2000 - it was VERY damaged. Deep scratches and paint leftovers deep in the wood, even after removing it with heatgun and paint remover.

Answer 1

You have to go over the wood again with medium grit paper at least. Finish the sanding job with fine paper if you still have the energy. Varnishing over wood that has only received a rough sanding will make sandpaper scratch marks stick out everywhere. Finishes highlight imperfections, so even though you may think the surfaces are smooth and ready for a finish, I guarantee that if all you used was a coarse grit sandpaper, they are not. Whenever you sand, make sure you only do it in the direction of the grain. When done sanding, go over everything with a vacuum cleaner and finally a tack cloth. All dust must be removed before applying a finish. You MUST tack cloth the surfaces. If using Varnish as your finish, then do not apply anything underneath. Just apply the finish to the raw wood. If using Polyurethane (which is what you should be using because Varnish takes a long time to dry and will therefore must likely give time for dust in the air to settle on the finish while it is still wet), I would put a thinned out (ie add extra denatured alchohol to it) coat of shellac on first as a sealer coat. You then put 3 coats of polyurethane on top of that. I'd use water-based polyurethane if I were you. It doesn't stink as much and goes on clear. Oil-based polyurethane goes on with a slight amber tone. By the way, shellac (even the one labeled as clear) also has an amber tone, so if you absolutely do not want any color change to the wood you are finishing, just use water-based polyurethane directly on it. However, if you don't mind a bit of an amber tone, shellac is absolutely the best sealer coat to put on wood. I'm a wood worker. I work with these things all of the time.

Answer 2

I'd have to suggest DO NOT wash after any sanding. All you'll manage to do is raise fibers in the wood conflicting with any notion you have of a smooth/clean surface to varnish over.

Sand again with a finer grit and use a TAC cloth.

You picked an intensely laborious task, but one that you should enjoy for years after. I wish you well.

Steven Wolf

Answer 3

When you have fine sanded, use fine wire wool to finish. Then, a vacuum cleaner. After your first coat of varnish, you will find that the wood fibres will have 'picked up'...it will feel rough. Rub down with fine wire wool, recoat...rub down....recoat to get the finish you want. Use a ronseal floor varnish over the lot!

Answer 4

If you don't want to get all tired, a random pattern electric sander will work. A circulare sander will cause swirl marks, and a belt sander is very aggressive and will cause and irregular suface if not carefull, more for shaping & rough sand. I wracked my brains for an alternative I didn't get anything. I don't suppose you need to plane it.

Answer 5

I,m surprised you sanded it with rough paper it seems to me if you wanted a smooth surface you would have used fine or very fine paper

Answer 6

yes, do med then fine end it with a 220 grit.you don't have to kill yourself like you did with the course sand paper all the hard work is already done.
as far as treating it goes you may want to bleach it.with a wood bleach , not laundry bleach.

http://www.woodcentral.com/bparticles/woodbleach.shtml
http://www.woodcraft.com/family.aspx?FamilyID=5535

as far as the finish goes id use polyurethane

http://www.minwax.com/products/protective/fast-poly.cfm