On 9/13/02 11:32 AM, "Jim Thursby" <athursby@tampabay.rr.com> wrote:
> Also be aware that over time, a coat of smooth-prime that was originally
> sanded with 320P one day after spraying will start to smooth over the
> scratch. In other words after a week your 320P scratch may now be 500P or
> 600P. It's still thru curing for a while. Point being, don't sand your parts
> on Monday with 320P and paint on Saturday and hope to have good adhesion.
> You may not. BTW I don't believe adding another coat of primer/sealer over
> your smooth-prime just before topcoating has any effect on adhesion. Your
> still putting a wet layer down with a mechanical bond only. If you are
> trying to hide multiple colors of primer or something then a sealer coat is
> wise, but not for adhesion. More wet coats can give you problems such as
> dye-back and solvent entrapment.
>
> James Thursby
>
> -----Original Message-----
> Behalf Of Fred Fillinger
> Subject: Re: Primer and Paint
>
> The difference on solvent paints, where wet-on-wet came up, is
> possible interaction of the solvents in primer and topcoat, plus
> locking in unflashed solvents by the top coat, but depending on how
> fast the topcoat cures. Water-bornes are different, with no solvents,
> as water can migrate via osmosis pre-cure. Don't they tell you not to
> wet sand unless really fully cured?!
>
> Everything you observed per below I found with System Three's
> water-borne, too. Once cured, only tooth adhesion rules. Something
> about how in the cross-linking process the molecules form chains for a
> new molecular structure that don't want to adhere to its own kind on
> subsequent coats.
>
> Best,
> Fred F.
>
> "Tony S. Krzyzewski" wrote:
>>
>> Re "wet-on-wet," the topcoat mfr's directions should control.
>>
>> I found that without applying wet on wet with Top Gloss I got inter
>> layer disbonding. My standard spray technique now is to mist on a light
>> coat, leave for 20 minutes and then spray another two coats at 30 minute
>> intervals applying as much paint as possible without getting drips (now
>> there's an art!).
>>
>> Absolutely essential with Top Gloss is a good tooth grip - nothing finer
>> than 320 grit. Miss a spot with the sanding or fail to clean it properly
>> with Prep Wipe and there's a good chance it'll break and peel back ....
>> just like the front area of the lower cowling that I painted last
>> weekend :-( If you have to respray the stuff then it's out with the 320
>> grit sandpaper before you spray.
>>
>> Another advantage of effectively building up one thicker coat is that
>> there is no opportunity to sand through a coat to expose the lower one.
>> If you do build up a multilayer finish and cut through the top layer
>> while finish sanding you'll find that there's a tidal mark which is
>> impossible to remove without painting again.
>>
>> I would also add that if you get it right then Top Gloss is very tough
>> and polishes back beautifully.
>
>
Hi Jim!
Could you give me your latest phone # or contact information? Best to
contact me directly at kpav@uia.net.
I helped Jim McGinnis get his airplane ready to fly and he needs help in
some initial flying. I have some ideas about this and would like to talk
with you about this specific circumstance. I offered to help him directly
but so much is going on in my life right now I doubt I will be able to get
together with him in a timely fashion. Can you help??
kp
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