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Lovegasoline 12-01-2009 11:30 AM

Skim Coat Tools? Knives, Trowel, or Magic Trowel??
I have plaster on wood lathe walls. A couple walls were poorly skim coated by a worker (pre mix green label joint compound + some plaster) and then primed with cheap Behr primer. The sanding job was poor and some screening and sanding marks are evident through the primer. I intend to do a VERY LIGHT SKIM COAT on this...not enough to build up the surface but to just fill in the sanding marks and add a thin glaze that I can sand back.

I will need to do some more standard skim coating here in the future (not with plaster...with either regular JC or quick set compound) and the tools I've used in the past are not sufficient. I see all sorts of approaches.

Can someone post a link ore recommend the specific tools used for skim coating? How wide a knife is generally used?

I see mention of broad knives. What exactly is a broad knife?

I have a 6" taping knife (flexible blade) and another about 12' knife (stiff rectangular blade). The former is too narrow to smooth out undulations in the wall and the latter doesn't feather very well.

What about a trowel, would that be better? Also, would it work for a VERY THIN SKIM, as mentioned above.

The other tool I've seen referenced is the 'magic trowel," a very wide (2ft?) squeegee like tool with a rubber blade, the edges of the rubber are apparently made to feather very well.

Any suggestions?

RickyBobby 12-01-2009 11:49 AM

I would use either a 10" or 12" drywall knife and Plus 3 compound (blue lid). The larger knife enables you to feather easier by adding more pressure on 1/2 to 3/4 of the blade. Plus 3 works well and sands easily.

Even if you cannot feather it out perfectly you should be able to sand it without a problem.

I have the same style wall in my current remodel and have done a lot of skim coating using this method with great success. This is tried and true with me so I wouldn't mess around with the magic trowel....although I did see it at SW this weekend.

Lovegasoline 12-01-2009 12:09 PM

I need some clarity on the knife.

There are huge range of profiles, materials, stiffnesses, and blade widths for a 12" knife. Stiff, flexible, short blade, wide blade....


RickyBobby 12-01-2009 12:32 PM

A 10 or 12" drywall taping knife is what you want. You mentioned you have a 6" taping knife already. This will be the same style, only 10 or 12" wide. The actual blade dimensions are approximately 3" x 10 or 12".

The blade is flexible and when pressed against the wall should easily flex. You do not want a stiff blade.

HD, Lowe's, Sherwin Williams all sell these. A decent 12" knife is roughly $15. I have one made by USG that I have had for some time and really like it. Hyde also makes a good one. The blade can either be stainless steel or blue spring steel. Either of them work fine.

Lovegasoline 12-01-2009 03:47 PM

I have a 6" knife, the steel blade is more or less a half-circle with handle attached, flexible blade.

I have a 12" knife. The rectangular Blade is about 12" x 4 ",, with a rigid metal support bar at the handle end of the blade...the support goes the full width of the blade. This blade isn't as flexible.

Are both of these taping knives?

bjbatlanta 12-01-2009 06:14 PM

They're called taping knives, but the "broad knife" (generally anything over 6") is used for bed and skim coats. I would recommend a 10" knife for a DIY'er. A little easier to handle than a 12. I personally don't care for care for the lightweight (Plus 3) type compounds. I would use regular ready mix. You will need to thin the mud to make it easier to spread. A cup or so of water to a 5 gallon bucket. Apply a thin coat and wipe back off. Allow to dry, sand, prime, touch-up (if necessary), and paint.

Paulie 12-01-2009 08:51 PM

Skim coating and feathering is learned skill. The better you get the less you sand. Most guys have a set of knives just for feathering large areas and they range from 10" to 16". Unfortunately there is no magic trowel/knife. Too bad.

Scott L. Fuson 08-01-2012 10:25 PM

For your skim coating of walls use a heavy nap roller and thin your mud to a good smooth texture. Roll on walls vertically like painting. Then knock down the mud with a Magic trowel either using a 12 inch,18,22 or 24inch. Get a spray bottle and mist knife and wall to get a real slick smooth texture.Do a section at a time always keeping a wet edge. Works great for me.

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