# Last coat - I think i did something wrong...



## borisw37 (Jul 28, 2010)

I applied 3 coats of cabot semi-gloss oil based polyurethane and waited about 5 days after the last one to make sure it cured. The finished looked good but inspired by all the you tube videos i decided to "finish" the finish. So 400grit > 600 grit + soapy water > 0000 Steel wool + rubbing compound.

Seemed like a good idea.. but the finish came out really dull. Much much duller than what it looked like before I messed with the 3rd coat. Looks like a milky film. The darker areas are not as dark anymore and the brighter areas are not as bright. I'm not trying to go for a mirror polish here, thus the semi-gloss. So the sanding was supposed to just level out the surface, knock down the tiny air bubbles and other imperfections.

The surface does feel very smooth and has that "rounded" feel. No sharp imbedded dust particles...

So what do I do now? I would like it to have a bit more luster to it.


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## Rob (Oct 31, 2006)

I don't think you will get passed semi-gloss; what you had before you began finishing the finish. Did you rub in between coats? 0000 wool isn't very fine when it comes to finishes. Rubbing compound also comes in many grits.
Bottom line is that it sounds like you didn't rub properly with the right stuff to get back to the 3rd coat finish.


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## rrich (Jun 24, 2009)

The difference between gloss and semi-gloss is that the semi has an additive to disperse light. 

Semi gloss or satin polyurethane must be stirred FREQUENTLY to insure even distribution of the light dispersing additive. If semi-gloss is not stirred frequently the second and third coats from the same can will have excess quantities of the light dispersing additive.

With multiple coats of frequently stirred semi-gloss, each coat is going to add more light dispersing additive to the finish. (Coat upon coat) At some point the finish seems to be just muddled.

Assuming that your intent is a three coat finish that will appear semi-gloss, the first two coats should be gloss. The third coat should be frequently stirred semi-gloss. The advantage to this method is if the final result is still too glossy, a fourth coat using semi-gloss is possible.


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## burkhome (Sep 5, 2010)

rrich said:


> The difference between gloss and semi-gloss is that the semi has an additive to disperse light.
> 
> Semi gloss or satin polyurethane must be stirred FREQUENTLY to insure even distribution of the light dispersing additive. If semi-gloss is not stirred frequently the second and third coats from the same can will have excess quantities of the light dispersing additive.
> 
> ...


 Rich is right on target. Also solvent based varnish is better for rubbing out than poly.


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## borisw37 (Jul 28, 2010)

Rob,
Yes I sanded with 320 between each coat. Used a tack cloth to remove every little bit of dirt before applying the next coat.

Rich,

I understand your point but:
- Instructions on the can said to use 2-4 coats of the same semi-gloss stuff
- The finish looked good except for a few brush marks bubbles etc... before I tried to rub it out.

I'm thinking of just sanding with 320 and putting on the 4th coat, then leaving it alone.


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## rrich (Jun 24, 2009)

How well cured was the poly?

Maybe let it sit for a week or two and completely cure and rub it out again?


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## cabinetman (Jul 5, 2007)

borisw37 said:


> Rob,
> Yes I sanded with 320 between each coat. Used a tack cloth to remove every little bit of dirt before applying the next coat.



Each coat should be totally cured. Using an impregnated tack cloth could present problems by leaving a residue. If you want to use a tack cloth try a dry microfiber one.

Your last coat may be acceptable. If not, a wet sanding with wet-or-dry silicone carbide sandpaper in a high grit (600x-1500x) with water (you don't need soap) will remove those finite imperfections. Sand with the grain.I would forget about the steel wool. You could use various rubbing compounds, from coarse (in the red family), to fine (in the white family). Automotive stores sell compounds in various grits, could be by the number.












 





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## borisw37 (Jul 28, 2010)

Yes, it was well cured. Sanding resulted in the fine white powder so it wasn't gummy or anything.
So I did some more experimenting. The overall process came out to be 
320 grit > wet sanding 600 > wet sanding 1500 > automotive buffing compound and then a lawyer of buffed carnuba wax. Came out looking very good. I still have the semi-gloss finish from the poly that I used, but the surface is very very smooth to the touch.


Cabinetman, so why no soap? I thought soap stops wet sand paper from sticking to the wood too much, collects dust particles better...?


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## cabinetman (Jul 5, 2007)

borisw37 said:


> Cabinetman, so why no soap? I thought soap stops wet sand paper from sticking to the wood too much, collects dust particles better...?



Wet sanding is done on the film finish, no bare wood should be part of that. Soap is unnecessary. I've tried it and it gives me a false sense of "smooth". Just plain water gives me a better feel of the surface being sanded.

I don't use wax, as its use can preclude further finishing.












 





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## rrich (Jun 24, 2009)

borisw37 said:


> 320 grit > wet sanding 600 > wet sanding 1500 > automotive buffing compound and then a lawyer of buffed carnuba wax.


Finally a lawyer that is good for something. :yes:


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