[AMC-List] Fw: A brief body and paint primer

["RetroRalph" <retroralph@xxxxxxxxxxx>]

I got this from a friend here in Oregon that is a member of the Alfa Club. 
I think it is worth passing on.
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Ralph Ausmann  -  Hillsboro, OR - > <ralph.ausmann@xxxxxxxxx>
http://mysite.verizon.net/res79g4m/ ... and "check the links"
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From: Richard Hiatt
To: ralph.ausmann@xxxxxxxxxxx

>From the Alfa bb website. I thought it was pretty interesting.
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                        Body Filler and Lead: One Man's Opinions


What is the best filler to use on my vintage car? I see this question many 
times over on many different sites, so I thought I would add my two cents in 
as a professional restorer.

First of all, let me explain that body filler, be it made of lead, 
aluminized reinforced polyester (i.e. All Metal or Metal-2-Metal), 
fiberglass reinforced polyester (i.e. Kitty Hair or Glass Lite), polyester 
filler (i.e. Bondo, Z-Grip, or Rage), or a glaze (i.e. Metal Glaze or 
Ever-Glaze) are all designed to do the same thing; smooth out small 
imperfections in sheet metal work. Each of them has there own strengths and 
weaknesses, which I will get into in a moment.

None of them are intended to fill large dents, more than a quarter inch 
deep. All of them, except glaze, are designed to go on top of bare metal. As 
well, some restorers apply them over epoxy primer with good results. 
Excepting glaze, they are not designed to be used on top of paint or most 
primers.

As in most things related to automobiles, the quality of the underlying work 
defines the quality of the final repair. Most horror stories regarding 
filler (i.e. Bondo) come the misuse of the product. You cannot use it over 
rust, existing bodywork, or apply it too thick and have a lasting repair. 
When used as intended, all fillers will last the life of the car.

In order to have a long lasting repair, they must be applied according to 
directions (I know, I know, but seriously, read the directions) and ALL rust 
must be removed. Any of these products used over rust will only buy you a 
few weeks or months and then the rust will return.

The manufacturers recommend no more than a quarter inch of applied filler. 
So, the sheet metal should be as straight as practical. What does practical 
mean? Well, if someone is doing a $2,500 complete paint job, it means doing 
as little sheet metal work as possible and slathering the car with filler. 
If someone is doing a $5,000 complete paint job, practical means all metal 
is finished to within a quarter inch overall. This is within the published 
limits of the polyester based fillers. If someone is doing a $10,000 paint 
job, it means getting the panels as straight as possible and using less than 
a 1/16 of inch of filler in small areas. While, I don't do it, I have seen 
shops use a reinforced filler to build up half-inch areas over a 2 foot x 2 
foot section and have the repair last for several years. The manufacturers, 
and I, are not recommending it, but I have seen it work.

There are several classes of filler: lead, polyester, easy-sanding, 
reinforced, and glaze.

Lead is the original filler. It is a non-ferrous metal (i.e. won't rust and 
a magnet will not stick to it) that melts at a low temperature and 
relatively (compared to other metals) easy to work. It's advantages are: 
when the paint is removed from a car, one cannot tell whether the repair was 
done at the factory, before 1970, or by someone who used original materials. 
For some, it comes with bragging rights, "my car has no Bondo, only lead." 
The disadvantages of lead are: it work hardens as the car vibrates and 
becomes brittle over time; it is less flexible and has less adhesion than 
modern polyester fillers; it is more expensive; it is more difficult to work 
than modern fillers; and, the fumes it puts off while being applied are 
toxic. Personally, I see no reason to use lead, other than someone wants to 
be original and recognizes that the repair will be more expensive and less 
durable than one done with modern materials. Unless you are painting your 
car in lacquer for originality sake you should really not be using lead.

Regular polyester filler (i.e. Bondo, 3M Lightweight Body Filler, etc.) is 
made of polyester and a bonding agent. It is light, easily malleable, 
flexible, and has a low tensile strength. The repairs will typically have 
pinholes and need to be glazed before finishing. When applied in a thin 
layer, it is extremely durable and strong. However, it gets its strength 
from the underlying sheet metal.

You can think about it this way, it is very hard to poke your finger through 
plastic wrap once it has been vacuum-applied over a product you buy. But, it 
is very easy to poke a hole in a roll of plastic wrap. The strength comes 
from the substrate.

Easy sanding fillers (i.e. Evercoat Rage Extreme, Z-Grip, etc) have 
hattonite or talc added to them to make them easier to sand and have fewer 
to no pinholes. Trust me, get this type of filler, it is much less work, 
even if it is more expensive.

Reinforced filler is a polyester-filler that has some sort of strengthening 
compound added to it, generally aluminum beads or fiberglass. All Metal and 
Kitty Hair are examples. This filler has a much greater tensile strength and 
is suitable to use in places where lead would have been used by the factory. 
There is a bit of a religious war as to whether fiberglass or aluminum beads 
are a better, but both are very strong and flexible. Neither product will 
leave a finished surface and will need to be skim coated by another filler 
and or glaze.

Glaze comes in a tube and is designed to fill very minor imperfections. 
Glaze unlike other fillers, can be used on top of existing paint and primer, 
so it can be used to fill small surface imperfections (stone chips, etc,) 
before a car is painted. It should not be used in large areas or as the 
basis for a repair.

The way I approach the work is as follows. I do not use an epoxy base coat. 
I repair and work the metal to within 1/32 of an inch overall, with the 
occasional 1/16 inch problem area. I apply All Metal (aluminized reinforced 
filler) in the problem areas and for covering weld seams and factory panel 
issues. I may or may not use some All Metal to slightly change the shape of 
panel openings (trunk area, door openings, etc). This is dictated by how 
perfect the car is to be. I personally prefer to not fix factory gap issues, 
but to each their own. After I finish with the All Metal, I will use some 
Z-Grip (easy sanding filler with hattonite) in areas with small undulations 
that I believe will not block out during sanding. I then prime the exterior 
surfaces of the car with a high-build polyester primer (I like Sherwin 
Williams primer). This is essentially like spraying 30 mils of polyester 
filler on the entire surface of the car. I block the living daylights out of 
the car, and hope I don't need a second application. I will then use Metal 
Glaze (glazing putty) on any small areas as necessary and then seal and 
paint.

I hope this is helpful for those trying to navigate the world of fillers. 
This is just my experience, I am sure others will chime in.

Good Luck,
Mike
        1974 Alfa Spider Daily Driver
        1965 Jaguar E-Type
        1977 Ferrari 308 GTB
        1965 Plymouth Sport Fury with a 426 wedge
Last edited by Vantaaj : 12-19-2005 at 05:21 PM.
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