Re: Touch-up paint quandary

On 8/2/2020 7:11 PM, VanguardLH wrote:
> 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.
> 

Thanks for the info. It's been a while since I used factory touch-up 
paint and at that time one had to shake the small paint container till 
the metal ball inside was freely moving in the paint fluid.

I am also suprised that I'd have to apply water to the tip as I would 
have thought lacquer thinner would have to be used.