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  • "Stearate" Treated Sandpaper

    I have been having some trouble recently with what I think are "fish eyes" in a clear, waterbased polyurethane finish. I prepared a test piece (happened to be cherry) which was sanded and then rubbed with a tack cloth sourced at an automobile finish supply store. I think this sandpaper is stearate coated. Can stearate cause the fish eye effect? I don't know what is in the tack cloth. Does anyone have any experience with contamination from a tack cloth? Thanks for any comments you may have.
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  • #2

    Re: "Stearate" Treated Sandpaper

    Re: "Stearate" Treated Sandpaper

    Originally posted by grant-s View Post
    Can stearate cause the fish eye effect? I don't know what is in the tack cloth.
    grant-s!

    Stearated paper can cause waterbased finishes to fisheye. It depends what type you are using. Most of the stearated or "no-load" paper sold for furniture finishing these days is very lightly stearated and causes no problems at all. I have been using Norton Adalox for 10 yrs and never had a problem. If you bought a product designed for automotive use then there could be a problem with the amount of stearate in the paper.
    Personally I would suspect the tack cloth as the culprit for the reason you stated. You never know what is in them. I don't use tack cloths, I blow off as much sanding dust as possible then wipe down with a lacquer thinner soaked rag a couple times. When scuffing between finish coats, I blow off the dust and wipe down with one of those microfibre cloths that you can buy at Costco in a packet of 20 or so.
    From your post it sounds as if you are sanding the wood with the stearated paper. If so, that's not a good idea as you could introduce contaminates onto the substrate (especially the grain) which could cause adhesion problems unless you use a sealer under the poly or wipe the surface with a strong solvent before applying finish.
    What type of poly are you using? Can you post a pic of the fisheye and tell us where it's located in relation to the grain? There are other things it could be and a host of cause for fisheyes, which range from deodorant residue to WD40 mist in the air, or handling wood after eating pizza to droplets from car exhaust spattering the wood. Tracking down the cause is a bit like an episode of CSI.
    Good luck...............Paul

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    • #3

      Re: "Stearate" Treated Sandpaper

      Re: "Stearate" Treated Sandpaper

      Just to add a wee bit to Paul's post, stearated paper is recommended by the books for scuff-sanding of a finish, but not sanding wood, itself. When scuff-sanding you are actually sanding varnish or shellac or whatever, not wood. When sanding a finish there is an assumption that the surface is smooth, so it won't catch and hold bits of the powder - it wipes clean.
      Mike in Orangeville, ON
      http://ifonlyyouwood.blogspot.com/

      SPCHT

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      • #4

        Re: "Stearate" Treated Sandpaper

        Re: "Stearate" Treated Sandpaper

        So I am confused ...

        From doing some net searches; Mirka BullDog Gold has a good following. When I look at Amazon (http://www.amazon.com/Mirka-23-615-0.../dp/B0000223T4) the tech details indicates "Made with anti-load stearate to provide increased life" while the product description includes "Premium paper for finishing as well as heavy stock removal"

        From the post above, you aren't supposed to be using Sterate sandpapers for heavy stock removal only for between coats ... but this is a 60 grit sandpaper. I can't image using that for between coating finishing but I can for removing a whole pile of wood.

        Somebody want to straighten me out?

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        • #5

          Re: "Stearate" Treated Sandpaper

          Re: "Stearate" Treated Sandpaper

          From what I understand, the "better" quality sandpapers ex Mirka, Norton 3x, Klingspor are supposed to be fine for water based finishes. I talked with Target coatings about this when I started using their products. I generally use a shellac sealer though so I can't say I've really tested it properly under worst case scenario.
          Paul

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          • #6

            Re: "Stearate" Treated Sandpaper

            Re: "Stearate" Treated Sandpaper

            Originally posted by CheapScotsman View Post
            So I am confused ...
            Why?

            Given that the OP gave no details of what type, brand or any other info on the products/techniques he used, a generalized reply was given. In general sanding wood with stearated paper has the potential risk of causing finish adhesion problems, unless a lightly stearated, high quality (eg Mirka, 3M, Norton) paper is used. I still think it's better to use aluminum oxide or garnet and is good practice to wash the wood with thinners before starting the finish process.
            What is posted on Amazon is a sales pitch. I have no doubt that if the manufacturers thought they could get enough people to bite, they would advertise the paper as a method of removing genital warts.
            Talking on the cell phone while driving is not a good idea either, but a lot of people take that risk and have no ill effects.
            BTW 60 grit stearated paper is great to level out orange peel or the craters associated with using Polystar but I agree, it's not your usual between coat sanding medium.

            Basically, it's a risk analysis, if you're informed, you make better decisions......................Paul

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            • #7

              Re: "Stearate" Treated Sandpaper

              Re: "Stearate" Treated Sandpaper

              Originally posted by Paul O in Paris View Post
              Why?

              Basically, it's a risk analysis, if you're informed, you make better decisions......................Paul
              Between all the info above and a re-read of the sanding pages in Flexner's book ... I am better informed now. Thanks very much.

              How do you know if sandpaper is "lightly stearated" as opposed to, I guess, heavily stearated?
              Last edited by CheapScotsman; 11-13-2008, 01:38 PM.

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              • #8

                Re: "Stearate" Treated Sandpaper

                Re: "Stearate" Treated Sandpaper

                I can't help with the stearate but here's a bit of info on tack cloths.
                Never use them folded. Open them fully then ball them up loosely and use like that. Regularly open it and ball it up again. Do not apply any pressure. Your hand should be at least 1" from the surface with the ball open between your hand and the surface. If you use it folded or flatten the ball with your hand, the heat from your hand will melt the sticky stuff in the rag and you risk contamination. I'm told the sticky stuff is bees wax. That info came from a CIL rep many years ago and they may be different now but they sure seem to be the same.
                J.P. Rap Mount Hope Ont.
                Carpe Ductum (Seize The Tape)


                "In this world, you must be oh so smart, or oh so pleasant." Well, for years I was smart. I recommend pleasant. Elwood P. Dowd

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                • #9

                  Re: "Stearate" Treated Sandpaper

                  Re: "Stearate" Treated Sandpaper

                  Originally posted by CheapScotsman View Post
                  How do you know if sandpaper is "lightly stearated" as opposed to, I guess, heavily stearated?
                  Good question.
                  These days I think all of the major sandpaper manufactures produce lightly stearated paper for the wood finishing business. Don't know about auto body stuff. Used to be that the heavily stearated stuff felt "soapy" to the touch and had a fairly stiff backing paper. I've used Norton Adalox and 3M Free Cut with no problems for many years.

                  Paul

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                  • #10

                    Re: "Stearate" Treated Sandpaper

                    Re: "Stearate" Treated Sandpaper

                    Most of the stereated sandpaper for the automotive industry is tinted so body shop guys can see where they sanded. Insert bodyman jokes here. It is very unlikely this is the source of your problem. The tack cloth is the most likely. Take a scrap board and cut it into a 4 or 5 peices. leave one raw, sand one, tack cloth one then finish them. If they all fisheye its on the wood or in the air, it only sanded or tacked you know what the problem is. Hopefully this is the case. If everything fish eyes you start your detective work. Elminate anything that could cause problems Wd 40 is often the worse one. Also watch your finger prints. If you do an oil change on the car then go to put the second coat on your table you see where I am going. The best one we dealt with was a 200 person furniture manufacturing plant. It took a month of detective work to narrow it down to the perfume one of the workers on the night shift wore.

                    Good luck.
                    Mark
                    www.masterfinishing.ca

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