sanding on the last layer of polyurethan varnish.

[Lasse Hilbrandt]

Im finishing a elm burl slap for a coffee table. First I applied pure tung oil and let it cure. Then I padded multiple layers of devaxed blonde shellac on untill I got a nice gloss finish. I want a gloss finish.

I now have two layers of water based polyurethane varnish on but I can see streaks/strokes from the brush in the surface.

I have ordred some micromesh pads ranging from 2000 grit up to 13000 grit.

Can I sand the streaks/strokes away with these and still get a gloss finish ?

[Scott Holmes]

Most water borne finishes are harder than oil based poly (which doesn't buff up to gloss very well due to it's toughness and lack of hardness). That being said which waterborne you used and how thick a film you built will determine the final outcome.

With sufficient build you should be able to rubout the finish to a high gloss. If this is your first rubout I will caution you to be careful near the edges of the project and don't over do it. use a back block to make sure you are making the surface flat. Flat and smooth are not the same...

FYI High gloss will highlight every flaw in the finish... satin will hide most minor flaws in the finish.

[Lasse Hilbrandt]

Most water borne finishes are harder than oil based poly (which doesn't buff up to gloss very well due to it's toughness and lack of hardness). That being said which waterborne you used and how thick a film you built will determine the final outcome.

With sufficient build you should be able to rubout the finish to a high gloss. If this is your first rubout I will caution you to be careful near the edges of the project and don't over do it. use a back block to make sure you are making the surface flat. Flat and smooth are not the same...

FYI High gloss will highlight every flaw in the finish... satin will hide most minor flaws in the finish.

So I should apply more layers before rubbing out ?

[John TenEyck]

I don't think the steaks will go away unless you sand down below them, especially if they are below the top layer. To rub out a finish you need a top layer that is thick enough so that you don't cut through it in the process. The way to get a thick layer is to apply enough layers fast enough that they form one layer. Someone just wrote an excellent explanation of this a day or two ago. But the short story is - apply each coat as soon as you can so that it burns into the one below. With the WB varnishes I use I can apply the next coat in about an hour. Once you have a thick layer built up from maybe 4 to 6 coats then let it cure until it's hard. Most WB products cure at least 90% in about 7 - 10 days. Then you can rub it out.

John

[Lasse Hilbrandt]

Arghh da***t I thought that only the streaks in the top layer was visible and that they could be polished away. Does that mean I have to sand everything down to raw wood again ?

[Scott Holmes]

No. Help us understand these streaks...

Are they brush marks aka ridges or are they something else?

If they're brush strokes (ridges) then you need to sand it flat as John stated... if it's something else; we need more info.

[Lasse Hilbrandt]

It is brush marks

[John TenEyck]

You don't need to sand it down to bare wood. Just sand it until it's flat, then apply enough coats of finish quickly enough to form a thick enough layer to rub out. You'll know when it's flat as the surface will have no low, shiny spots and it will be a uniform dullness everywhere. No need to sand beyond that.

John

[Lasse Hilbrandt]

Thankyou very much

[Lasse Hilbrandt]

If I want to do the melt in method, how do i know when I can apply the next layer ? how many layers should be sufficient ?

[John TenEyck]

Apply the next layer as soon as you can scuff sand the layer below w/o it gumming up your sandpaper. If there are no dust nibs or defects you don't need to sand out, then apply the next layer as soon as you can touch it without your finger leaving a print. How many layers? Hard to say as it depends upon how you apply the finish, the % solids in the finish, etc, but I'd say at least 3 coats, and likely more.

John