Polishing with Micro-Mesh


khairy1974
12-19-2008, 02:49 AM
Hi all....

First of all, i am a beginner in modelling...picking up this hobby in my early thirties.....

My biggest question is:-
How do I sand the body of my car without sanding the edges....
This comes after the paint job have been completely removed after sanding...
I am using Micromesh...and is there any tricks/tactics in doing the sanding?

klutz_100
12-19-2008, 03:14 AM
Use he micromesh/sanding paper wet, rub lightly, cover edges with strips of masking tape before sanding and use smaller pieces to rub in tight/awkward places.

There is nearly always small amounts of burn-through in my experience but these are usually easily fixed.

It's worth reading this very good talk-through by CFNet HERE (http://www.cifesystem.com/911-1.html)

MPWR
12-19-2008, 10:14 AM
In my experience, there are no real surefire secrets or tricks to using micromesh. Taping edges can help, along with vigilant use of caution, but as klutz_100 points out it seems nearly impossible to escape with paint covering all edges and corners. Some people seem to be better at avoiding it than others, but it is truly an endemic problem with micromesh. It's further exacerbated by the fact that paint is simply not as thick on edges as it is elsewhere- most paints (lacquers especially) pull away somewhat from edges- so the paint there is thin before you start grinding it.

Micromesh seems to be frequently presented as the one and only way to create a perfect shine on a painted body- but it simply isn't true. There certainly are other ways of going about it, that yield equal or superior results to micromesh. Personally I hate the stuff, and haven't used it in years. By spraying smooth layers of paint and then polishing with a less aggressive agent (I use Tamiya coarse compound), it's much easier to avoid burning through edges.

It takes some practice and experience, but you will find a system that works for you. You may eventually find that you can get micromesh to work as you want it to, or you may find a better way of doing it- but don't consider it to be the only path.

CFarias
12-19-2008, 05:35 PM
PART ONE: THE RIGHT TOOL FOR THE RIGHT JOB...

I have done three things to virtually eliminate any rub-thru. I've cut the micro-mesh cloths down, found a more practical foam bar, and use harder paints.

The cloths that you get in the micro-mesh system are unnecessarily large. Examine your cloths closely. Chances are you are only using the edges of the cloths for polishing so there's no point in having such a large cloth. Besides the lack of sensitivity you get if you haven't cut them down greatly risks your chances of rub-thru. Using a brand new blade and a metal ruler, cut them in half, then half again, then half again. You will have eight pieces that although they are smaller, are adequately large enough to polish large areas of your model like the hood or roof.

Cut down the foam block also. Use a raiser saw and slowly cut thru the block until you've cut a piece small enough for the smaller cloths to wrap around. Consequently you will now have a more pliable foam block which will in turn greatly enhance your sensitivity to the contours of your model, thus reducing the chances of rub-thru. You can also visit an auto paint store and purchase a professional foam block. The one I have is about 1 cm thick and has a soft gray foam backed by a harder black foam. These are ultra-sensitive to body contours.

Finally, for the body I use automotive grade paints almost exclusively. They have many advantages to hobby paints including that they are relatively very hard and these polish easier. I also clearcoat my models. This enhances the appearance of the paint and also provides a tough shield against rub-thru. It will also warn you when you're about to rub through the paint. As you polish you will see a white powder on the cloths. This will turn to your body color as soon as you've rub through the clear and alert you that the paint is now being rubbed off.

Some might find cutting the cloths difficult to consider, but if you can not use them without bad results then they are useless the way they are. I pay about $20 for my set and throw away the used cloths after five models. This means that I spend about $0.50 on polishing cloths per model.

CFarias
12-19-2008, 05:55 PM
PART TWO: IT'S ALL IN THE WRISTS...

Preparation and good techniques are key to getting a good finish.

Before you put on your first coat of primer, examine the body carefully. Plastic tends to "pucker" along panel lines and near the edges of the body of the model. This means that the plastic will be slightly raised near door and trunk line and so on. These areas will have thinner coats of paint and, compounded by the fact that paint receeds from sharp edges, will make rub-thru almost a certainty. Presand these areas with files and/or sanding sticks.

Sand each coat after it dries. Not sanding primer and color coats will make for very large orange-peel, a texture that naturally occurrs in sprayed paint. Having larger orange-peel will mean using a gritier polishing cloth in your initial pass which will also make rub-thru more likely.

Don't use the heavier sanding cloths unless you have to. I rarely start with anything gritier than 3200 and use the 2400 and 1800 for rubbing off nibs from the airbrushing session.

Don't rub too hard. You should only provide enough pressure to hold the cloth in place and not to rub the paint. Rubbing harder won't make the job go that much faster and will probably result in scratches left behind that the lighter cloths can't get out. A wet sanding technique and a light touch is the key.

Polishing takes a long time so be patient. The first pass with the cloths is simply to level the paint and this is the longest part of the system. Afterwards the subsequent passes with the lighter cloths will go by quickly, but don't expect to get it done all in one night.

Make a mental note of the parts you will expect to have problems with. Polish those areas first and work your way towards the easier areas. That way if you screw up then you've done it early instead of a couple hours into it.

Polishing is labor intensive but the results will have you forgetting about how bad your elbows hurt afterwards.

Finally, MPWR makes a very good point. Don't be afraid to try other ways of polishing paint. Find a system that works best for you.

Hope this helps.

Didymus
12-19-2008, 11:50 PM
I'm with MPWR on not using MicroMesh. It's expensive, unnecessary and it just invites burn-through.

Tamiya Coarse compound will do the job if the paint is applied smoothly in the first place. For problem areas, careful wetsanding with 1500 or 2000 grit will work just fine. You'll still want to follow up with Tamiya Coarse (it's not really coarse), Fine and Finish grades.

One good reason for clear coating your car bodies is that it helps prevent burn-through. When color appears on the polishing cloth, you know you've polished through the clear coat and it's time to stop and re-coat the area. Unlike a lot of people, I don't sand my color coats (Tamiya TS series) except where there's severe orange peel or another problem.

Ddms

Some_Kid
12-20-2008, 04:09 AM
Right off the top of my head I know of one way you can avoid rub-thrus. I have micromesh pads and they are pretty nice imo. However to be completely safe i recommend clear coating whatever color is underneath whether it is a solid color or metallic. Make sure you spray several coats of clear with good coverage. Don't make it too thick, but not too thin. Try to lay the best clear coat you can with minimal orange peal. You can try sanding the base coat with fine grades of sandpaper to help with orange peel. You could even use one of the micromesh pads to do this.

Once the clear fully hardens use a good rubbing compound(3m, tamiya etc) to remove all orange peal. You will have less risk in deep scratches while removing orange peel at the same but it is also alot more work and takes more time. I can't guarantee that you can remove the orange peel completely but you should get most of it.

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