Home>Discussions>INTERIORS>Molding & Carpentry>Sand paper clogging with thick brown substance
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Dave Male
Sand paper clogging with thick brown substance

I am sanding some very old , 50 plus years, 12" wide barn wood that was used for a floor. It is pine and one inch thick.

My attempts to sand it both with rotary and belt sanders have been an expensive exercise in clogged sand paper.

Starting with 36 grit, the surface of the paper quickly becomes clogged with a brown substance that is very warm to the touch, then cools quickly to a hard solid surface.

It does not come off the sand paper and clogs the paper after only a few square feet.

Any thoughts?

Re: Sand paper clogging with thick brown substance

Surprised a barn had finish (e.g. poly) on the floor, but looks like it did. I believe that's what you're seeing. A larger grit might not clog as much. I've run into this many times and just assume it's the cost of the job. Then again, not sure how much you're sanding. I'm usually sanding a table top and deal with it. Looks like you might be using this again for a floor. Will look awesome. You might rent an industrial size sander for floors if that's the case. Given it's pine, even though I'm handy, I might opt to hire someone to sand and finish the floor.

Planing might be another option (but it looks like the floor is already down). Not sure if planing the finish also clogs the planing blades, but assuming if it does, they can be unclogged.

Anyone else have a comment?

Nancy Lewis
Re: Sand paper clogging with thick brown substance

Did you find a good solution to the thick, gunk that accumulated on the floor and the sanding discs when sanding? I was sanding an old floor yesterday, and the relatively smooth floor I started with ended up with hard gunk deposited on it in several places. Sanding with coarser grit(20) wasn't a solution - I finally scrapped it off manually with a metal scrapper. However, I have four more rooms and a hallway to do.

Re: Sand paper clogging with thick brown substance

it looks like shellac to me, that was a common product years ago for sealing floors. shellac is wax based and thats where the problem lies it gums up the drums on the sander.

im surprised the rental shop didnt tell you to wash down the floors a few times with T.S.P. it will help break down the dirt and grim along with some of the wax so that the sanding drums will last longer.
just as an example, well i sanded my floors 2 years ago, washed em down with tsp 3 times. once finished i spent about $310 for the rental, sanding drums, discs and polyeurathane. a buddy did his place the same month and went straight to sanding, he spent over $1000 in supplies and rental. mind you i get rental gear much cheaper do to pro rate but that only would have made a difference of $100. he just kept burning through drums like crazy

Re: Sand paper clogging with thick brown substance

It is almost sure to be shellac. I have had this problem several times and the only solution is to use denatured alcohol and steel wool/rags to clean off the shellac before you sand. The friction of the sandpaper on the floor produces heat which then melts the shellac onto the paper. Shellac is not wax based but is actually the resin secreted by an insect called a lac insect. There is actually a very tiny amount of wax 3 to 5% which comes fro the lac insect It is actually harvested off of trees that the insect habitates in India and dissolved in denatured alcohol to create shellac. Denatured alcohol will remove the shellac. Its a tedious way to remove shellac but I did it for most of our house and it does work. Make sure that there are no pilot lights or other open flames as denatured alcohol is flammable.

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