Using a cone filter to strain old finish - Woodworking Talk

mixer440 · 10-24-2009, 02:39 AM

More often than not, when I get down near the bottom of a can of finish, there's a lot of particles mixed in.

I've heard that you can't use a cone (paper) filter to filter out the junk from finish that has flattening agents (matte, satin..etc), because the it would filter them out as well......making it a gloss finish.

I called around and got mixed answers from people telling me yes and no to this.

Myth or truth?

Tony B · 10-25-2009, 08:58 AM

Quote:

Originally Posted by mixer440

More often than not, when I get down near the bottom of a can of finish, there's a lot of particles mixed in.

I've heard that you can't use a cone (paper) filter to filter out the junk from finish that has flattening agents (matte, satin..etc), because the it would filter them out as well......making it a gloss finish.

I called around and got mixed answers from people telling me yes and no to this.

Myth or truth?

Part Myth part Truth

Under the proper conditions, the flattening agents are very fine and suspended in the finish and should not be able to be strained out. However, under the wrong conditions the flattening agents settle to the bottom and kinda gel together and form a gooey ball (I love using technical terms). All it takes to change the 'conditions' is a good stirring and I mean a really good stirring. If you strain out the flattening agents you didn't stir enough. As a matter of opening my shop everyday, I stir all of my 5 gal cans that have been opened. I dont really have to but if I need a satin or flat finish all I have to do is give a light stiring and not spend a lot of effort getting it right. I keep a long stirring stick nearby leaning against the wall.
If on the other hand you do have a gooey mass on the bottom of a stick placed in there, then yes, it will be somewhat glossy.

Streamwinner · 10-25-2009, 09:33 AM

Depending on the finish you are using, you can always use post-finish sanding to get the flattening you desire, such as using 0000 steel wool.

mixer440 · 10-29-2009, 02:27 AM

Thanks all, but everyone missed the point probably because my question wasn't clear enough.............but, here's the scoop.

The myth (as reported by many manufactures and users), is that if you try to strain a satin or matte Polyurethane or Lacquer finish you will strain out the flatterners. These flatterners which disperse the light, are many times silica particles dissolved in the liquid.

Therefore, you'd essentially turn a satin finish into a clear one.

Well, I just used a typical paper cone filter with a medium mesh and there were no problems whatsoever. Not only was I able to filter out any contaminants in the liquid, but there was no difference in the look of the finish.

Tony B · 11-01-2009, 04:47 AM

Quote:

Originally Posted by mixer440

Thanks all, but everyone missed the point probably because my question wasn't clear enough.............but, here's the scoop.

The myth (as reported by many manufactures and users), is that if you try to strain a satin or matte Polyurethane or Lacquer finish you will strain out the flatterners.

I didn't miss the point, you didn't read it right. I stated "Under the proper conditions, the flattening agents are very fine and suspended in the finish and should not be able to be strained out."
BTW, I have never seen anything by a manufacturer stating that you can strain out the flattening agents. What I have seen though is warnings about stirring well to make sure the flattening agents dont settle to the bottom.

cabinetman · 11-01-2009, 05:06 AM

There's no guarantee that those gooey globs at the bottom are what you think they are. Straining them out to achieve a certain sheen is less than an accurate method. No degree of predictability.

Tony B · 11-01-2009, 11:27 AM

Quote:

Originally Posted by cabinetman

There's no guarantee that those gooey globs at the bottom are what you think they are. Straining them out to achieve a certain sheen is less than an accurate method. No degree of predictability.

I agree 100%. I believe some of that gobby gooey stuff is the solids that actually make up the lacquer itself. The rest is thinners and the vehicle.