Need finishing advice

Discussion in 'Newbie' started by Paul A Andrews, Mar 11, 2017.

  1. Paul A Andrews

    Paul A Andrews

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    I've been turning bowls for about four years, all in Arizona in the winter (Canadian snowbird). Due to health issues we sold everything we had in AZ and spend winters at home in Ontario now. I really miss the big wood shop in AZ which had a lots of turners and lots of mentors. I built a shop in my house and I now belong to an AAW chapter called Thames Valley Woodturners Guild in London. All that is pretty exciting. The guild has a mentor program which I have used and made a great connection with a guy who has been doing this for 40 years and knows all the tools and techniques.

    The shop in AZ had its customs and most of the turners used Mylands sanding sealer and Mylands high friction build finish. They have worked OK for me but I have a feeling I would get better results changing things up. I would prefer not to finish on the lathe and while the Mylands had the virtue of quick, finishing time is no longer of the essence to me and I have lots of patience for taking a week or more to do finishing. I have a buddy who is into cutting boards and I asked him how he finishes. He uses Watco Butcher Block finish without applying a sealer. So I thought I would give that a try and bought some of that finish yesterday. The issue I have is should I put a sealer on first. Now I'm doing this in Southern Ontario which is very humid in the summer. We had a record number of days in the 90s last year and when it is that hot here everything sags in the humidity. I need to make sure all my pieces are protected from swelling/cracking. Will the Watco product seal my work or should I seal it first? A long way to ask a short question but I hope the colour helps.
     
  2. Mike Johnson

    Mike Johnson

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    Can you store your wood bowl turnings in a humidity controlled environment?
    Each wood type seals differently depending on the wood sealer and applications applied.
    A small room or enclosure could be setup with a small dehumidifier to regulate humidity.
    This would help in controlling the final drying process in a high humidity environment.
    You could start the drying process in your uncontrolled shop area and then move the
    pieces into the controlled drying area to complete the drying process.
     
  3. Paul A Andrews

    Paul A Andrews

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    Mike, I don't really have a problem with humidity in my shop. Winters are normally very dry (although with the changing climate this winter has been quite mild and they are trending that way) and the humidity level in the shop runs in the 40s. The hygrometer is showing 42% as I write and I'm happy with that. I run a dehumidifier all summer and that keeps it in the 50s. So I don't really have a drying issue associated with finishing. My concern is that I don't know where my finished product is going to wind up after I sell or perhaps gift it and I don't want changes in humidity to cause it to deform in any way so I have been sealing everything. The question is will the Watco product seal the work. Again, thanks for responding. I appreciate it.
     
  4. Owen Lowe

    Owen Lowe

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    Sealing is a misnomer. Unless you encase the piece in a heavy coat of plastic the wood will still move with humidity changes. The degree and speed to which the wood absorbs or loses moisture depends on the permeability of the finish. A butcher-block finish is usually very thin without much body. It is intended to be refreshed regularly after use and cleaning. Varnish, polyurethane, and lacquer build thicker barriers that don’t need to be refreshed except to repair damage.

    I use wipe-on varnish, either Tried and True brand or a 3 part home-made mix of varnish, linseed oil, and naphtha. Three wiped-on and rubbed-off coats are all I put on. I don’t notice much seasonal movement as far as the bowl rocking on its feet, but I know they do go slightly oval on occasion.

    Remember, you can’t stop the moisture gain/loss, only slow it down to minimize the high and low swings between the seasons — unless you go the encasing route.
     
  5. Paul A Andrews

    Paul A Andrews

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    That's very helpful Owen. I guess the Mylands 'sealer' (that's what they call it) really just reduces the permeability of the wood by 'filling' it. Maybe I'll try putting the 'sealer' on first and then two or three coats of the butcher block. Or maybe I'll just take the Watco back to Home Depot and get some varnish or polyurethane. I appreciate your help.
     
  6. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Paul,

    Owen made an excellent point about humidity and wood movement. I'll add that the purpose of sealers is to prep the wood for a film finish topcoat such as varnish or lacquer and not to make it impervious to humidity changes. The Watco Butcher Block Oil & Finish is not a film finish ... it is an oil that is designed to soak into the wood (mostly Stoddard solvent and mineral oil). If you had previously applied a sealer to the wood, it would block the oil finish from soaking into the wood so you would wind up with a non drying oily film sitting on top of the sealer. My preference is to stick with just one kind of finish on a piece because there is unlikely to be much cumulative benefit of layering different kinds of finishes and there is a risk of making a mess.

    I rarely need a sealer under a finish, but when I do, I can make my own sealer by thinning the film finish. A sealer can be useful when dealing with porous or punky wood.

    The bottom line is that once wood has dried to EMC, seasonal humidity changes don't result in significant movement in turned items. If you apply a finish before the wood has thoroughly dried all bets are off regarding warping or cracking before it reaches EMC.
     
  7. Paul A Andrews

    Paul A Andrews

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    Bill,

    I'm beginning to absorb (no pun intended) the advice. I've never paid much attention to the chemistry of finishes, just done what I was told. You and Owen have really opened my eyes and I appreciate it. I think I'll take the Watco oil back to the store and get some varnish or poly. I've never been entirely happy with the results from Mylands high friction build finish and I'm looking forward to making changes. You've been a big help. The AAW forums are worth their weight in gold. I checked out your gallery. Beautiful work! I liked all of it but I particularly related to the mesquite bowl with turquoise ring. I made a similar bowl a couple of years ago in AZ attempting to make a replica Southwestern clay bowl. Using the embossing powder was fun and I intend to do some more of that. I like cats too, I just like dogs better. Thanks for your help.
     
  8. Paul A Andrews

    Paul A Andrews

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    By the way Bill, what is EMC?
     
  9. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Equilibrium Moisture Content. It's when the wood has dried to the point that it is in equilibrium with the local environment and can't lose any more moisture. In a desert that might be about 6% and in a humid location it might be 16%. An EMC of 10% to 12% is typical for air dried wood in most parts of the country. An excellent book for woodturners who want to understand the "how's" and "why's" of wood characteristics is "Understanding Wood" by R. Bruce Hoadley. There is also a lot of excellent information in the Forest Products Handbook by the USDA Forest Products Laboratory which is available online.
     
  10. odie

    odie

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    Paul.....Bill is our helpful "technical adviser" on these forums.....:D

    .....and he does quite a bit of research to clarify thoughts, ideas and concepts we discuss here.

    Other terms you might hear, are "seasoned", "stabilized", "air dried", and a few more. These terms all mean essentially the same thing as EMC.

    On the other hand, kiln dried wood or KD, often has a lower MC than the ambient environment will allow if air dried.....but, not always. I've purchased wood claimed to be KD, but my meter shows up to 14%! Most KD woods I've purchased are in the 8-12% range though. On a rare occasion, I've had a few that registered as low as 6% MC. I guess it all depends on whose kiln, and whose moisture meter we're talking about.....:rolleyes:

    ko
     
    Last edited: Mar 14, 2017
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  11. Paul A Andrews

    Paul A Andrews

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    ko and Bill, very helpful. I'll probably find the suggested book. I definitely would be more comfortable understanding what I'm doing. FYI I just bought Varathane at Home Depot. Probably sold in the US but I don' really know. The HD guy told me Its basically a water based polyurethane with a different trade name. Crystal clear so it enhances but doesn't alter the colour of the wood. I plan to leave the 'sealer' on the shelf. The little bowl I just finished was from a blank which had a bit of a coating of something on it so I was concerned about MC. However my handy dandy meter said 9% so we were good to go. Thanks again for your help.

    Paul
     
  12. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Varathane was my favorite varnish when I used to do flat woodworking. That was several decades ago and Flecto was the manufacturer. Now, regardless of the brand, everything is made by either Minwax, Rustoleum, or Krylon. Back then Varathane didn't have a water based varnish and the ones that were available weren't very good and were difficult to apply. I'm sure they are better now, but those early bad experiences really gave me a bad attitude towards water based varnishes. I will stick with finishes that I trust.
     
  13. john lucas

    john lucas

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    I never use a sealer. I tried for a while and didn't see any advantage to it. Sometimes on functional pieces I might thin the first coat of finish to get it to penetrate more. On user bowls I use Mike Mahoney's walnut oil and usually don't thin that just apply several layers over a couple of days. My normal finish for most things is either lacquer which I spray on, or minwax wipe on poly. I live in Middle Tennessee which is about as humid as any place during the summer. I have some problems with my lacquer on the really bad days but all the other finished I've played with work fine.
    I am not a fan of friction finishes. I just don't feel that they hold up and on larger pieces it's hard to keep them from streaking. Their only real advantage is you get an OK finish in a hurry. Most good finishes take time. Really good finishes take a lot more time.
     
  14. Paul A Andrews

    Paul A Andrews

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    Right on John, and that's why I'm moving away from the friction finish. Thanks for your comments.
     

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