Re: Touch-up paint quandary

Cameo <[email protected]> wrote:

> I'd like to fix some minor scratches on my car with a dealer supplied 
> touch-up paint set, but this one came with only pictoral instructions 
> without any narrative. It's mostly self-explanatory though, with some 
> exception, at least for me. I thought maybe some of you can help me out 
> with it. I am including a scan of the pictorial here:
> 
> https://i.postimg.cc/XvfdtRfK/Touch1Up.jpg
> 
> My quandaries start with pic. 1 and 10, which I interpret as "no 
> shaking" instructions. I find this odd, because I would expect just the 
> opposite. Pic 4 shows applying the base coat and pics 6 through 8 
> perhaps repetition of the same. Then after that is dry, pic 10 shows the 
> application of clear coat. Am I getting it right?
> 
> Thanks for any help with this.

My guess is:

 1. Do NOT shake the bottle of base coat.  That would add bubbles of 
    air.  It is a thick paint.  You don't want bubbles in the paint job.
 2. Apply base coat between temperatures of +5 to +35 (Celsius).
 3. Clean affected spot (no mention what to use - guessing isopropyl 
    alcohol).
 4. Apply base coat.
 5. Wait 10 minutes to let dry.
 6. Apply water to tip.
 7. Press tip onto dried base coat.  Rub around to absord excess paint.
 8. Rinse off tip of absorbed base coat.
 9. Wait 10 minutes to dry.
10. Do NOT shake bottle of clear coat.  That would add bubbles of air.  
    It is a thick paint.  You don't want bubbles in the paint job.
11. Apply clear coat between temperatures of +5 to +35 (Celsius).
12. Dab on some clear coat.
13. Wait 20 minutes to let dry.
14. OK, you're done with the paint job.
15. Wait 48 hours to let paint harden.
16. Use the polishing compound to blend.  Buff off polishing compound.

Touch-up paint is a lot thicker than what you get in spray cans.  That
is to prevent the paint from sagging since you are brushing it on
instead of apply a multiple to thin spray painted layers.  While you can
shake water-based paints because they're thinner to glide onto the
surface, the same would happen if you shake enamel paint which adds
bubbles, and you'll end up painting bubbles onto the surface.  If enamel
paint has separated its oil from the pigment, you fold the oil into the
paint using a stirrer stick.  You don't shake the can or whip up the
enamel paint.  Alternatively you can use a mixer paddle attached to a
drill at low speed.  The end is dipped into the paint, and then it
spins.  Since the paddles are under the surface, there is no air to mix
into the paint.  You're just moving the settled pigment and oil
together.  For a small cap-size quantity, you can remove the brush and
head shell from an electric toothbrush leaving behind just the vibrating
rod to stir the paint.  You want to fold the oil into the pigment.  You
don't want to fold in any air.  Depends on what surface effect you want.
If you want a glass surface, keep out the air.  If you're using a paint
roller, well, that adds texture, so air isn't a problem.  I doubt you
want any paint on your car to look like it was applied with a roller.

You never want to paint over rust even if you don't see any.  I would
use 1800, or higher (3000), grit sandpaper to prep the paint chipped
spot.  Then apply rust converter (aka rust reformer which is water
soluable tannic acid with organic polymer) paint.  The tannic acid
converts the rust (iron oxide) to stable (inert) iron tannate, and the
polymer acts as a primer layer.  The idea is not to polish down to shiny
metal since the intention is to convert unstable dusty or flaking rust
into smooth stable iron tannate with a primer.  You just want to get rid
of any dusty or flaking rust, and to make for a smooth surface to have a
smooth paint job.  If you polish down to bare metal, there's no rust to
convert, but you'll need to use a primer before the base coat.  Rust
convert doesn't work on aluminum, galvanized metal, stainless steel, or
copper.  It needs to be iron or steel (but not stainless).  Even if
there is no rust (that you can see), rust converter is still a good
primer for the base coat.  Takes 2 to 4 coats of converter to build up a
decently think primer layer.  The thinner the converter solution, the
more coats are needed.

Most seem to come as a spray can (to cover large taped-off areas), so
I'd spray into the cap to puddle it up to dab into the paint chipped
spot with an ear swab (while spinning the tip to keep cotton filaments
from coming lose and stuck in the paint, or use a small tip paint brush
and wipe excess off with rag and reapply with a 2nd coat).  Wait however
long the converter paint says to let harden (1 hour between coats, 48
hours to harden).  Use the high grit sandpaper to prep the paint for the
base coat paint.  Then I'd apply their base coat.  The rust converter
paint is sufficient.  Adding the base coat and clear coat is for looks
(to hide the paint chips by masking with a similar color paint and
similar depth of sheen).

Drying time depends on temperature and humidity (and, of course, some
airflow over the paint).  The recommendations are you don't apply the
next paint layer until the last coat has dried to the touch.  However,
if you touch the paint to test and it's still tacky, then you just left
a fingerprint in the not-yet-dried paint.  It's your call as to when the
paint has completely dried and ready for another coat.  Also, when
applying another coat, it "wets" the prior coat.  I've run into the
problem that I thought the paint was dry but was impatient in waiting.
Yeah, it seemed dry, but the next coat sagged.