Author Topic: Issues With First Coat of Finish  (Read 965 times)

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Offline Avery_J

  • Posts: 2
Issues With First Coat of Finish
« on: March 22, 2020, 12:58 AM »
I recently made my first chair out of walnut and after applying a coat of Osmo I noticed a few issues. The first coat looks and feels a bit waxy after drying, so I did some research and found that I may have sanded the wood with too fine of grit, I went up to a 320 grit sandpaper before I applied the first coat. I also noticed some visible scratch marks on the chair that I would like to fix.

I'm thinking about resanding the chair and reapplying the finish but if I do that do I need to start at a lower grit or can I go straight to a 180 grit (or whatever is the best final grit for walnut)?
« Last Edit: March 27, 2020, 02:52 PM by Avery_J »

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Offline ktb153

  • Posts: 36
Re: Issues With First Coat of Finish
« Reply #1 on: March 22, 2020, 06:27 PM »
I've only used Osmo a few times so I'm definitely not an expert but every time I've used it the waxy feel took a few days to go away. I'd try sanding the scratches out in those areas with the 320 and then doing a second coat before you sand the whole thing. Osmo is a very forgiving finish as long as you apply it in thin coats

Offline WarrenT

  • Posts: 22
Re: Issues With First Coat of Finish
« Reply #2 on: March 22, 2020, 07:22 PM »
Let me share an Osmo observation that I noticed while applying it to a cherry dining room table project that I am just finishing up.

I used a No 5 bevel down then a bevel up smoothing plane to flatten some minor highs and lows after the glue up of the table top.   Then I sanded the top of the table top in a few stages up to 220 grit.  I did not bother sanding the bottom. 

When I applied the Osmo to the bottom, I noticed it was much more difficult to work the oil into surface that was freshly smoothed by the planes.  When I worked the oil into the top, it went fine, but I probably could have used something a touch more coarse than 220 paper.

As mentioned above, the wood will feel less waxy after a few days.  I am always patient with the Osmo, giving it at least 48 hours between coats.
« Last Edit: March 22, 2020, 09:24 PM by WarrenT »

Offline Avery_J

  • Posts: 2
Re: Issues With First Coat of Finish
« Reply #3 on: March 25, 2020, 09:58 PM »
Will do! Thank you.

Do you have any advice on how I can make sure the resanded spots have the same finish shade as the rest of the chair? 
« Last Edit: March 27, 2020, 02:52 PM by Avery_J »

Offline HotSauce

  • Posts: 11
    • 4 Chicks Furniture & Wood Art
Re: Issues With First Coat of Finish
« Reply #4 on: March 31, 2020, 09:47 PM »
We almost exclusively use Osmo on our tables. We sand to 280 and quit. We really pay attention for swirls and other sand marks before finishing. I use a LED light and go over every inch of the table before we finish. Applying Osmo too heavy is usually the cause of it still being tacky after 24 hours. You really have to work it in. Think skin lotion. Then apply a second coat after 24 hours. You can go over the surface with a nylon pad (sos pad) before the second coat for a smoother finish. It took me a good 3 big projects before I felt really comfortable with it. Now, it's out go-to as well as Odie's Oil. Good luck!
 
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Offline deepcreek

  • Posts: 906
    • TimberFire Studio
Re: Issues With First Coat of Finish
« Reply #5 on: April 01, 2020, 12:33 AM »
I use Osmo Polyx Oil on almost every project.  I generally sand to 180 with an ETS 150/3 and 220 on end grain with a RTS 400.

If it still looks waxy or wet a few minutes after applying, wipe it off and buff it out with a clean cloth.  I use Brawny paper towels.  Lint isn't an issue because the finish is in the pores.  Change paper towels frequently.  I fold them in quarters and go through a roll per project.  If you leave Osmo on the surface, it dries glossy and on top of the wood.  However, it is NOT a build finish.  It's supposed to be a penetrating finish.

Festool's STL 450 surface control light is outstanding to apply raking light for inspection.

Osmo does have special instructions for Walnut if it's likely to be exposed to water like a table top.

FINISHING WALNUT WITH OSMO POLYX OR OSMO TOP OIL

The Osmo Polyx Oils (3054 and 5125) and Osmo Top Oil (3058) all provide a beautiful & durable finish on the many varieties of Walnut. It must be understood, however, that the grain character of this wood, regardless of variety, grade or cut, causes it to require special preparation and/or application to ensure proper protection from water-spotting. Water-spotting on oil-finished Walnut is because of the physical characteristics of Walnut, not failure of the oil or oil/wax finish.

Failure to understand and follow the below is likely to cause water-spotting to be an ongoing issue with any Walnut table, cabinet, flooring or other surface subject to liquid exposure.

Walnut is known as a semi-ring porous grain wood. Translated into lay terms, this means that it has bands of very fine pores or pits through most of the wood. These pores appear to be just the right size to readily wick water. Our best understanding is that the cured oil/wax finish cannot ‘bridge’ or ‘block’ these pores enough to counter the wood’s natural tendency to wick water. (Remember, these pores transported fluids from leaves to root and back during the tree’s life.)

These pores must be ‘grain-filled’ or ‘stopped’ PRIOR to or during finish application to achieve satisfactory resistance to water-spotting. Many woodworkers will probably have their own techniques for managing this characteristic.

We know of two techniques to achieve this goal:

1: Use a wood filler of the brand and color of your choice using standard filler application and sanding techniques. A possible objection to this technique is that Walnut color-changes over time, whereas the filler probably won’t. Another possible objection is with Claro Walnut, which can exhibit more color variation than American Black Walnut; it may be harder to match with available fillers. Filler is probably the only choice with Walnut flooring; flooring contractors will be quite familiar with the process. Standard application techniques for the Osmo product of choice are then used.

2: One can also use a modified application technique with the Osmo product to achieve the same goal. It is probably not practical for flooring. Along with significantly decreasing the water-spotting, the below technique can create a beautiful polished luster that is hard to achieve with our standard application techniques.

After sanding the surface to the desired dry grit, use wet-dry sandpaper wetted with the finish to abrade the surface of the Walnut to create a fine ‘slurry’ of sanding dust and finish. With the wetted paper, work the slurry into the grain structure using some vigor. Buff dry with clean cotton cloths before the slurry begins to get sticky.

Choice of sandpaper grit is up to the finisher, although 220 grit is likely to be the coarsest available in wet-dry form. There are many choices in finer grit, but be aware the higher the grit, the glossier the end result.

One should plan on two or three coats using this method, using 220 or finer to choice. No brushed coats are required.
Remember, all oil-soaked rags, paper, gloves etc are self-combustible and require proper disposal to avoid risk of fire.
Allow the finish to cure for at least two weeks in normal interior conditions before covering or exposing it to water.

Care and maintenance are the same as with other techniques.
« Last Edit: April 01, 2020, 12:44 AM by deepcreek »
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TimberFire Studio
Houston, Texas

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Offline Birdhunter

  • Posts: 2991
  • Woodworker, Sportsman, Retired
Re: Issues With First Coat of Finish
« Reply #6 on: May 26, 2020, 08:47 PM »
Just curious, but what is the advantage of Osmo that makes it worth all this work?
Birdhunter

Online CeeJay

  • Posts: 67
Re: Issues With First Coat of Finish
« Reply #7 on: May 26, 2020, 09:26 PM »
A good Osmo finish is beautiful and durable. Easy to repair. While the product is expensive the key to a good finish is to use it sparingly so it goes a long way.

I’ve found that after a fine sand it can help to spray it with water to lift the fibres then knock it back with fine grit paper before letting it dry and applying first coat. That really helps with letting the wood absorb the first coat. Use it really sparingly, wipe off excess, then buff. Very light high grit sand, then repeat for second coat (without the water spray obviously).


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Offline mrFinpgh

  • Posts: 379
Re: Issues With First Coat of Finish
« Reply #8 on: May 26, 2020, 10:39 PM »
My first couple projects with Osmo, I went to 320, applied with a white pad as if I were french polishing, and buffed everything off with shop towels within minutes.  This worked okay.  What I have found is that it really does seem to take up the finish a little more evenly and consistently if I don't go so high in grit.   

Now I stop at 150 or 180 and spend some w/ a mirka hand sander just to ensure all the scratches are running w/ the grain.  The results seem a little better to me.  I still buff off pretty aggressively after a few minutes of working it in.

From what I recall, a lot of the hardwax oil manufacturers TDS recommend something between 120 and 220 as a max grit. I wonder if it is has to do w/ the way the finish bonds to the wood?