Mixing Mud for Skim Coat

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mokid

mokid

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What are the secrets for mixing (or applying it to car)? I have tried several ratios of harderer/filler in the mix, but it always dries with a sticky surface that clogs sandpaper at first. I can rub baby powder on it before doing any sanding and it helps, but there must be a better way. It seems to be cured and hard enough to sand below the initial surface. I have heard guys talk about coating an entire car with a "skim coat". I'm just doing a few panels. The way it's going for me doing an entire car would be a real mess. All comments appreciated.................tx............james
 
I'm no expert, but I have only heard of fiberglass cars done in a skimcoat (correctly).
 
Dude, you need to knead the mixture more, if your using two part body puty, (aka mud), i usually use just enough harder to change the mixture into the color of the hardner, although lighter in color, i think thats why your getting hard on the bottom and the "fuzzy" on top, just play with it and you'll see what i mean... just remember, the more the hardner, the faster it sets up, and the worse it can get! And as far as "skim " coating, thats usually the last step in body work, you "skim" over the small imperfections and block sand it to make it perfectly straight, and yes it can take several coats!
 
in my experience with filler, I found that to much hardener can give you that "stickyness" and to little can sometimes aswell.

also it depends on how long you hardener has been sitting, I like to squesh the hardener around in the tube to get it mixed up some prior to putting it on the "mud".

normally if you scoop out a small pancake sized amount of "mud" a 1"-2" bead of hardener is plenty enough to do the trick.

I have dealt with it before and know what you mean about it being a hassel.

normally I just rub some bondo dust into the sticky surface and let it harden up a few more minutes and then come back and start sanding...once you bust through that first sticky layer its normally smooth sailing.

maybe someone here can have a better explanation as to why this type of thing occurs.
 
Cheap or old bodywork products tend to have poor results.

I'd go to your local autobody supply store, change to a high quality brand of filler/hardner and clean off your mixing board well and start over...........follow the tech sheet
 
Are you using putty "honey" if you are doing a skim coat? Sure makes applying skim coats a lot easier and way less pinholes. Also use evercoat "rage gold" filler to start with. Great to work with and sands easy.
 
Skip skim coating the entire car with filler, I would use a polyester primer like feather fill.
 
Seems like it's not mixed well at the bottom of your pallet. Try leaving a thin layer on the pallet (or mixing board or mixing pad, whatever). also if you are mixing your filler on a pourous surface like cardboard, it can mess up the last little bit. I friend who is a pro body man told me to put a few drops of fiberglass resin in when you mx up your gob. I haven't tried it yet, but he swears by it.

I don't see anything wrong with a skim coat on the whole car as long as you are willing to go to that expense, spend the time, use a LONG board and sand 95% of it off, but may be unnessesary for a driver.
 
AdamR said:
Skip skim coating the entire car with filler, I would use a polyester primer like feather fill.
Click to expand...

+1

at the shop I work at we use transtar poly primer, fills GREAT! In the long run it will save you money vs filling everything with a glaze or such, normally If we have to do any 'skim coatings' its with glaze and Evercoats metal stuff is expensive as hell around $25 a bottle, its insane.
 
Whenever I have had the problem of the sticky top of the filler I usually just keep an old piece of sandpaper around, scuff up the top, then once that is gone you can go back to your long board or block with a nice new piece of paper. It's sort of a catch 22, working filler you want to take it off as quickly as possible. So doing some sanding while the filler is still soft is a good idea but does tend to clog the paper. When I say quickly I mean with a sharp grit paper, that cuts the filler off fast. The faster you cut the filler off the easier it will be to get straight. The more sanding you make yourself do is what will create slight dips as worn out sandpaper tends to ride the high and low spots vs. cutting them down.
 
why not use a glazing putty like Icing,Half-Time,Dolphin,Metal-Glaze,e.t.c. there are dozens of them, none will have sticky surface if mixed properly and they are made just for that, to skim over pinholes and scratches,

I would not take a chance of mixing not enough hardener or adding some junk into the filler and year later have problems showing in the paint
 
I was using new filler (Dynalite), but an old tube of hardener.......threw it away and started using a new one..........problem solved. thanks for all the feedback.......james
 
I use Z-Grip made by evercoat it has IMO and thiers the best adhesion properties and sands easy. If you want you can add polyester resin to it to thin it out or cause it to "flow". If you add resin you MUST incsrease the amount of hardner. Feather fill is a great product for the $$$ it really fills and sands easy. Make sure your final prime is done with a good high build primer I use PPG NCP 270 it fills well shrinking is minimal and has great adhesion.
 
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