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MLC Polarion and Red Oak

Leo G

I've got a project that I'm spraying Polarion on Red Oak. I'm not looking for a full fill finish. I just want a nice finish like I would get spraying a conversion varnish.

What I'm getting is a surface that is full of high and low spots and pin holes because of the deep grain of the Oak.

I've tried quite a few different things. So far I haven't gotten past using the sealer. It's properly catalyzed (20oz sealer, 4oz of catalyst) and I add another 1oz of the reducer.

After that didn't work I thinned it to 30% so it would flow into the grain. It basically did the same thing as the 5% thinning. After that I did reducer and retarder (50 50) at 30% and after that I did 30% retarder. Still, without putting on a ridiculous mil thickness it wouldn't flow.

I tried a wet on tack coat and all that does is accentuate the highs and lows of the grain, it won't flow into the low grain areas.

Next I figure on going the opposite way and just keep doing 2 mil wet coatings, let it dry the hour, sand and repeat.

Anyone have any pointers for me? I'm using a Kremlin 10.14 with a 06-114 tip. Liquid 35psi and air 16psi with the trigger pulled. Basically my standard for most clears.

12/30/15       #2: MLC Polarion and Red Oak ...
Paul Snyder  Member


Leo - I could not find a tech data sheet for this product - it must be new to the market.

Are you using a sanding sealer before the topcoat? That's usually the best way to get a great finish with 2K-PU on wood.

12/30/15       #3: MLC Polarion and Red Oak ...
Leo G  Member


Yes Paul, I am using their sealer.

I have the PI sheets, I'll upload the PDFs if the site lets me.

Click the link below to download the file included with this post.


Click the link below to download the file included with this post.


Click the link below to download the file included with this post.


12/30/15       #4: MLC Polarion and Red Oak ...


Would it help to take and wipe or squeegee the sealer coat into the oak, let dry, sand and spray? This might fill some of the grain and pin holes, while not getting too heavy a build.

Not sure if it would give you the look you want, but a conventional spraying schedule does not seem to be doing that, either.

Just trying to help.

12/30/15       #5: MLC Polarion and Red Oak ...
Leo G  Member


I didn't use a squeegee to move it around but I did do something similar.

I sprayed on a 2 mil coat and then took a fine bristled brush that was in a cup of the Polarion retarder and I brushed across the grain and then with the grain to push the sealer into the grain pockets. Then I finished the box coat with another 2-3 mil coat. It looked like it would work, but it didn't.

Currently I am trying a different method. Thinning the Polarion sealer 30% and applying a 2 mil coat. Just enough to wet the wood. It sinks/absorbs in pretty well and has little build. Sand it and apply the sealer at 10% thinned at 2 mil again. This will have a fair amount of build. Sand it back hard and then go to the Polarion top coat, two 2 mil coats sanding between coats.

We'll see if it's acceptable. Since I was just playing with the sealer in the beginning I based the flow on the way the sealer reacts. The top coat seems to have better flow out properties. Hoping this will make it work.

On maple it's 2 seal coats and done, ready for the topcoat. I'm sure I could do one seal coat and 2 top coats. I just hadn't cracked the top coat can at that time.

12/30/15       #6: MLC Polarion and Red Oak ...
Paul Snyder  Member


Thanks for the data sheets Leo. Unfortunately they don't shed much light on this situation though... the sealer and top coat seem nearly identical according to the description, the viscosity, and the solids content. The VOCs is a little different.

The sealer has a high solids content, even though the viscosity is low, which contributes to the ridged build-up around the pores. Thinning it enough to avoid the build-up reduces the solids content down to the wash-coat thickness - not enough to give you a good base for the top coats. That means you'l have to spray an extra coat or two of thinned sealer which drives up the cost of the finish a lot.

The properties of a good sealer are excellent flow, leveling, adhesion, and sand-ability. The TDS for the sealer doesn't say anything about easy sanding which is unusual, and from your description it sounds like it doesn't flow and level well.

Personally, I'd switch to another product instead of trying to make this one work in this situation. ML Campbell may tweak the formulation over time and get it to work better with ring porous woods or they may simply recommend a different product. For now, the Eurobuild high solids sealer is probably a better choice with oak. If you're open to trying new products, the LBA-38 sealer from Milesi is exceptional.

You should be able to spray one coat of sealer, sand smooth easily, and apply two top coats and get great results consistently. Any extra fussing is not worth the effort/time/money.

1/6/16       #7: MLC Polarion and Red Oak ...

MLC products are NEVER the best in their class. They cheap out on the grind of their resins. If a good quality PU sealer is the size of sand, the MLC will be the size of gravel. this is why you get pin holes in some finishes and not others.
Ever spray MLC crystal? looks awesome the day you spray it, go back in a couple of weeks. Where did the finish go?

1/12/16       #8: MLC Polarion and Red Oak ...

Whats the grit sandpaper that you used as a final ? is there a stain involved ?

1/12/16       #9: MLC Polarion and Red Oak ...
Leo G  Member


120 grit, Mirka Gold on a Ceros.

No stain.

5/8/17       #10: MLC Polarion and Red Oak ...
David Kelsh Member

I have recently had similar issues spraying a mahogany top... specs sheets claim sealer and topcoat to be around 30 seconds on the Ford cup... in actuality I was getting 50 secs. I used the reducer and got best results spraying at 23 seconds, holding the gun a little further away than typical and lighter application than usual....noting that "usual" means nothing when talking spray techniques on a thread...
Oh yeah, I also went through LOTS of 320 grit sanding discs to flatten previous "experiment" coats.

Also noticed a 2000 grit abralon pad on a pneumatic orbital (wet sanding) will knock down the gritty feeling left behind from the solvent pockets evaporating.

Much more difficult than spraying MLC Krystal or Duravar

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