Ultra-Noob Finishing Question

[gsmittle]

When/How does one use sanding sealer and/or wood conditioner????

I just finished a couple of books on finishing (heh) and I'm confused....

Thanks,

old g.

[Tom Miller]

Not hugely knowledgeable myself, but one reason to use a sanding sealer is ensure an even appearance for a finish. Some oil finishes and/or stains may appear blotchy -- moreso for some woods (e.g. cherry and maple) than others -- if applied directly.

Here's how a sealer works in my mind:

A sealer is applied first, and then sanded down. Areas where the wood is less porous will not have much sealer penetration, and much of the sealer will be sanded off. When you apply the finish here, the sealer won't impede its penetration very much.

More porous areas will have deeper sealer penetration, and so more sealer will remain after sanding. When you apply the finish here, the sealer will impede penetration more. The end result is a more even finish.

I like using a thinned coat of shellac (1/2# - 1# cut) -- make sure it's dewaxed if you plan to apply anything over it.

Regards,
Tom

[SARGE..g-47]

Tom nailed one reason, meatloaf. The denser wood will not allow as much penetration as the soft wood in a given species. Stain will penetrate deeper and cause blotching (spotting). End grain should always be sealed as it will turn very dark.

It serves a couple of more purposes also. It will help seal in resins contained in the wood itself and keep it from rising and penetrating the surface to blend with your chosen finish after the fact.

And last, but certainly not least if you use water based stains or finish; the water in it will have a tendency to raise the grain (little furry nibs sticking up everywhere.. oooohhh :>) ...) which is not the smooth and what you were trying to achieve. The sanding sealer (or you can just use dis-tilled water wiped lightly on) will pre-raise it and you let it sit till it drys. That raises the grain and then you sand off those hairy nibs (always with the grain at this final stage) before you apply the stain or finish.

Hope that helps un-lock some of the mystery. Lots to learn, but like any jouney, one step at a time till you get there.

Regards...

[mdutch]

Finishing is NOT my forte, but I know this about wood. When you wet it (with finish or any liquid) it raises the grain, lifting up the fibers of cellulose made from the walls of the fractured cells where the face of the wood is cut or sanded.

Once the grain has been raised and sanded out, it will not significantly roughen again.

You can use a sanding sealer to raise that grain and "lock" it in place, then sand it smooth and apply your finish.

David Marks on Woodworks often uses WATER in a spray bottle to raise the grain of sanded wood, then lets it dry and re-sands it before applying his signature tung-oil finishes. The advantage is the water evaporates completely, whereas the sanding-sealer closes the pores preventing stain or finish from penetrating the wood. The water-method allows a penetrating finish to be used after the "post-grain" final sanding.

That may be only partly correct, but that's my story, and I'm sticking to it.

[SARGE..g-47]

What you stated is correct, mdutch. I hate to keep re-hashing the subject, but feel it is important to mention that the Water should be dis-tilled like you buy at the drug-store in the gallon jugs. Regular water is rich in minerals that will penetrate wood and cause problems latter. The dis-tilled has been boiled off to get rid of the minerals.

Regards...

[gsmittle]

Thanks for the info, guys. I'm much better at beginning than finishing, so I'm trying to catch up in that regard.

No longer quite as confused,

g.