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January 30, 2004
From: amukdigiphoto [mailto: amukdigiphoto@... ]
Sent: Friday, January 30, 2004 5:34 AM
To: midgetsprite@yahoogroups.com
Subject: [midgetsprite] Re: Paint Advice
Duncan
I'm not familiar with the base coat/clear coat system, although the last
time I
ordered some cellulose gloss from my paint factor, they did ask if that was
what I wanted, as thats the alternative to the 'all-in-one' system that I'm
most familiar with and use. The all-in-one system contains the pigment and
the gloss, and the high shine is slowly built up by successive coats,
flatting
back inbetween. To achieve the very high shine, you let the paint fully
harden
(4-5 weeks) then use a gentle rubbing compound on it and a rotary buffer.
Regarding etch primer, you can get away without using it, but in my
experience if want good adhesion to bare metal you need to use an etch
primer first, then primer/filler. I guess if the bare metal surface is
'roughed
up' enough you can get primer/filler to stick to it, but I prefer using
etch
primer first.
Yes, the term 'double-coat' does refer to a second coat before the first
coat is
dry. You wait for the first coat to 'flash off' (kind of semi-dry - still
tacky)
which takes between 5-15 minutes depending on temperature, then you
spray your second coat. I'm not really sure why 'double-coats' are used,
but
it certainly saves on flatting back, which takes long enough as it is. I've
then
flatted back between every 'double-coat'. You can flat back once the paint
is
'air-dry' which usually takes anything between 30mins - hour depending on
temperture.
My aim was to get about 5 or 6 (thinners/paint 50/50 mix) 'double-coats'
on,
flatting back between each double-coat, 2 or 3 (70/30 mix) double coats,
again flatting back between each double coat and a couple of (90/10 mix)
finishing double-coats, with a final flatting back before the last
double-coat.
You should aim for about 10 or 12 in total 'double-coats' for a durable
finish,
you can get away with less - up to you.
Regarding spirit wipe, I tended to spirit wipe the bare metal before the
etch
primer, a spirit wipe after the final primer/filler coat and before the
final
colour coat. You should probably spirit wipe after flatting each
'double-coat'
but I just found that the spirit wipe took so long to dry/evaporte (several
hours) it was almost defeating the object as more and more dust
accumulated on the paint surface which meant another wipe down before
painting with a dry cloth. In warmer temperatures you won't have this
problem, but you'll get other problems like the paint drying almost as soon
as
it hits the surface !
Another useful aspect to the spirit wipe is that it almost replicates the
'high-gloss' finish you'll get when the colour coats go on, so if you're
quick
(before it dries) you can have a good look at the panel for any defects
like
dings, dents, depressions which show up very well when in a 'gloss' state.
Another word of warning - the matt surface of primer/filler flatters to
deceive, its very good at hiding surface defects due to its matt finish -
you
just cant see them, which is why Guy mentioned in his post about 'guide
coats'. A guide coat is a light spraying of usually the colour coat, or any
paint
darker than primer/filler. The idea is to flat back through the colour
'guide-coat' revealing any raised areas or depressions. The ideal is to
flat
back to primer, but any high areas will be flatted back to bare metal in
some
cases, and any depressions will hold the colour coat - showing you exactly
where the problems are.
I developed my own 'system' to solve two problems. Rather than using dark
'guide-coats' I just put in a little amount of the gloss into the
primer/filler and
sprayed this. The first problem it solved was, as it was a different shade
to the
primer underneath, I could see exactly where I was spraying and was able to
fully cover the panel. The problem with spraying successive coats of primer
filler is because they're the same colour - you just can't see how much
you've
covered and where you havent been. As this coat was a different shade to
the
one underneath, and had a semi-gloss appearance it acted as a guide-coat
when I was flatting back - so I could see where the problems were. I kinda
liked the duck-egg blue colour of this!
I could go on and on, but I think its best to let you digest all of this!
Nigel
christopher_valentine@... 28796
Posted on January 30, 2004 03:16 PM
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