Sanding after primer and before paint ?????????????'s.
01-10-2002, 03:11 AM
#1
Safety Car
Thread Starter
Sanding after primer and before paint ?????????????'s.
I am going to be shooting my primer soon. I am going to be going to purchase some supplies tommorrow. Lars' paper says to sand with 600 after priming and before paint. I happen to have a whole ream of 400 from when my dad used to paint pickups. Can I use that or is it too course? Also, do I have to sand the primer sealer before I shoot the K36 primer surfacer?
Justin
Justin
01-10-2002, 03:26 AM
#2
Burning Brakes
Re: Sanding after primer and before paint ?????????????'s. (Dalannex)
I think you want to block the surfacer with 400 (will cut faster and straighter) and wet sand with 600. As for the sealer, I thought it went on over the surfacer after it was blocked and wet sanded, usually in the booth just prior to color. Might want to check with the paint supply store to get specific instructions for the system you're using.
01-10-2002, 03:29 AM
#3
Safety Car
Thread Starter
Re: Sanding after primer and before paint ?????????????'s. (ORVette)
I am going off of Lars' tech paper, and it says the sealer goes on first, then the surfacer. This is my first time around this painting business, so I don't know for sure. I'll ask the paint guy for sure as well. It is all PPG stuff that I'm using. Oh yeah, the paint guy said he would never reduce the primer sealer, and Lars' paper says it can be reduced by 25%. Somebody please tell me more on this.
01-10-2002, 03:46 AM
#4
Burning Brakes
Re: Sanding after primer and before paint ?????????????'s. (Dalannex)
I've never worked on fiberglass either, so I guess I'm kinda lost too. The sealer then surfacer order probably has something to do with the raw glass sucking up surfacer. Ther will most likely be another sealer to go over the surfacer after it's wet sanded to give the color a base to adhere to. Are you using single stage or base/clear? I used PPG Global System base/clear on my Monte Carlo 2 years ago and it still glows, AND it sits outside year round(1 car garage). Two thumbs up for PPG.
01-10-2002, 08:49 AM
#5
Le Mans Master
Re: Sanding after primer and before paint ?????????????'s. (ORVette)
The only thing that I did to the DP50 before I sprayed the K36 on was to hit a few areas that had hairs sticking up with a grey scotchbrite pad. I only waited about an hour before I sprayed the K36. Then I guide coated the K36 and let it sit overnight before block sanding. It sands great.
01-10-2002, 09:01 AM
#6
Melting Slicks
Member Since: Nov 2001
Location: Casa Grande AZ
Posts: 2,214
Likes: 0
Received 0 Likes
on
0 Posts
Re: Sanding after primer and before paint ?????????????'s. (Dalannex)
The problem with getting info about paint application is that it's more of an art than a science. That's why you will get conflicting stories about how to put it on. Everybody has some different little thing that they do. Two painters can use two different techniqes and end up with the same quality of paint surface.
I rarely sand my final primer coat finer than 400 grit and I've never had any problem with it. I too will add or subtract thinners to certain products or thin differently than the PPG guy says to. It just depends on what works for you. Of course you have to do a few jobs before you can figure that out!
I've found that when using a new product for the first time it's best to go with the manufacturers suggestions. Then if you run into a problem you know it's not something you did.
If I was to suggest a PPG paint product right now, I would say to use DBU base with Delta clear. This stuff is incredably easy to apply. Compared to shooting Acrylic Enamel or even some of the other clears, it's a dream. Of course others will disagree - that's the nature of the beast!
I rarely sand my final primer coat finer than 400 grit and I've never had any problem with it. I too will add or subtract thinners to certain products or thin differently than the PPG guy says to. It just depends on what works for you. Of course you have to do a few jobs before you can figure that out!
I've found that when using a new product for the first time it's best to go with the manufacturers suggestions. Then if you run into a problem you know it's not something you did.
If I was to suggest a PPG paint product right now, I would say to use DBU base with Delta clear. This stuff is incredably easy to apply. Compared to shooting Acrylic Enamel or even some of the other clears, it's a dream. Of course others will disagree - that's the nature of the beast!
01-10-2002, 09:13 AM
#7
Drifting
Re: Sanding after primer and before paint ?????????????'s. (Dalannex)
After you prime your car, get a can of krylon in a contrasting color, example, if your primer is gray, get a can of black. Spray a fine mist over the car before
you do your block sanding. By doing this, you will be able to find any low spots that you may need to fill.
you do your block sanding. By doing this, you will be able to find any low spots that you may need to fill.
01-10-2002, 02:07 PM
#9
Instructor
Member Since: Jun 1999
Location: Canton, Ga
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Re: Sanding after primer and before paint ?????????????'s. (shamby)
I used Lars instructions on my 69 and it is coming out great. I have just applied the final coat of primer and will
sand it with 600 if it thaws out sometime soon. Lars paper is under C3 Tech Tips.
Also when I bought the PPG stuff, I got a print out of instructions for the Sealer and Primer. It is about 3-4
pages and include what you can put over each one of them and how compatible they are..be sure to ask your
dealer for it. Good luck
sand it with 600 if it thaws out sometime soon. Lars paper is under C3 Tech Tips.
Also when I bought the PPG stuff, I got a print out of instructions for the Sealer and Primer. It is about 3-4
pages and include what you can put over each one of them and how compatible they are..be sure to ask your
dealer for it. Good luck
01-10-2002, 02:29 PM
#10
Safety Car
Re: Sanding after primer and before paint ?????????????'s. (TR69)
This question came up when I painted my vette too. The guys at the PPG place thought I was crazy for not putting the sealer last. But Lars knows what he is talking about, and many cars have been painted his way. My guess, the K-36 is such high quality stuff, it doesn't need to be sealed and is designed to be applied just before the base. If you put sealer on top, it might defeat the purpose and cause uneveness. Thats what the k-36 is for, to level it out.
01-10-2002, 02:45 PM
#11
Advanced
Member Since: Jan 2002
Location: Plantation FL
Posts: 97
Likes: 0
Received 0 Likes
on
0 Posts
Re: Sanding after primer and before paint ?????????????'s. (71,454,4spd)
Haven't painted my vette yet, but have done other project cars including a 65 stang fastback, on which I used the same PPG sealer/surfacer paint combo on that one very successfully. The sealer is epoxy based and mean't as just that...a sealer between the body panels and the finish layers. Really important for bare metal panels. The K36 is meant to go under the basecoat, although if you sand thru the k36 in spots, the sealer is a good idea. But you can still spot prime with k36 here also. Most importat is a smooth CLEAN surface before paint. If you've done it right, you will have plenty of sealed & primed surface for paint. But ask Lars if you can...he is the man...Just my .02
BTW, nothing against the paint store people, but I've gotten some not so good advice there also. Best of all, follow the Mfg recommendations.
[Modified by SteveA, 6:47 PM 1/10/2002]
[Modified by SteveA, 6:48 PM 1/10/2002]
BTW, nothing against the paint store people, but I've gotten some not so good advice there also. Best of all, follow the Mfg recommendations.
[Modified by SteveA, 6:47 PM 1/10/2002]
[Modified by SteveA, 6:48 PM 1/10/2002]
01-10-2002, 03:29 PM
#12
Safety Car
Thread Starter
Re: Sanding after primer and before paint ?????????????'s. (SteveA)
Here is the email I recieved from Lars today.
I am going by what Lars says. He knows this stuff, and others have had great success using his methods. Looks like I'll be buying a reem of 600.
Lars, I appreciate your help on this, and believe me, the hard and heavy question period is just beginning. In about another week, once I get the shop cleaned out and set up for paint and am ready, I'll be like a human question howlitzer. :D Be prepared. :cheers:
Oh yeah, is the 48 hour window the same on all layers, from sealer, to primer, to base to clear? I ask be cause work may interfere with this process a little. We'll have to see. Would I be able to spray all of it in a 2 day period?
[Modified by Dalannex, 1:33 PM 1/10/2002]
Justin -
Saw your questions on the primer/sanding issues. I can't post
replies to
the Forum from work (something to do with the firewall here), so
you might
post up the following response to your questions for people to
see:
First, the 400 grit wet is too course for the final wet sanding
prior to
finish painting. After cure and shrink-back, you will be able
to see
400-grit sanding marks in the finish. 600-grit is the coarsest
grit you can
use without having any problems with seeing any marks. You can
use a little
400 wet to do some rapid cutting down of thick spots in the
primer, but you
need to finish it off with the 600.
On the primer/sealer:
PPG recommends that the DP-series epoxy products be used in two
ways:
DP is used as an epoxy primer/adhesion base right over the bare
substrate
before you start doing any body work/filling/fill priming. On
metal cars,
this provides a sealed surface to prevent any corrosion (fill
primer is
porous, so it does not seal the steel from moisture
penetration). On 'glass
cars, the epoxy prevents any topcoats/primers from reacting with
the
composite underlayers, and creates a stable surface to work off
of. You
then apply the fill-primer (K36 or equivalent) over the top of
the DP. You
must topcoat the DP within 48 hours, or the DP will "seal up"
and you will
not obtain adhesion. If you go past the 48-hour limit, you must
scuff-sand
the DP to break the surface prior to priming over the top of it.
Once you have primed and sanded the car using K36, and you have
guide-coated
it and final sanded with the 600 wet, PPG recommends that the DP
be reduced
as a sealer and shot over the K36 (I can FAX you the PPG
DP-series data
sheet where they define and describe this technique if you'd
like. Your
paint supplier should have the data sheet where it recommends
this
technique). Reduced 25% with DT reducer, the DP becomes a
paint/primer
sealer rather than a primer. This thin coat of epoxy seals up
the porous
K36, and provides an excellent adhesion base for the basecoat.
It also
keeps the basecoat from possibly reacting with anything
underneath, and it
covers up any sand-through spots in the K36. You do not need to
sand the DP
sealer as long as you shoot your basecoat/clearcoat within the
time "window"
for adhesion. However, I find that I like to go over the DP
lightly with a
little 600 wet or a ScotchBrite pad just enough to pull the dust
"nubbers"
out of it and to produce a perfect surface. DP does not sand
well, and will
plug up your sandpaper quickly, so just knock the dust out of it
and then
shoot your basecoat. If you let the DP sit for more than 48
hours, you need
to scuff the entire surface up with ScotchBrite prior to paint.
When wet
sanding prior to paint, use cold water: Use of hot water for
sanding or
rinsing tends to cure and "skim" the surface. Use of cold water
tends to
leave the exposed "pores" in the sealer open for maximum
adhesion.
I have shot several non-show quality cars where I have not
sealed the entire
car with DP prior to basecoat. I have used the DP reduced as a
sealer only
to touch up sand-through spots in the K36, and then shot
basecoat directly
over the K36. I have not had any problems with cars shot like
this. But
PPG recommends the sealer step method in all of their
literature.
Lars Grimsrud
Saw your questions on the primer/sanding issues. I can't post
replies to
the Forum from work (something to do with the firewall here), so
you might
post up the following response to your questions for people to
see:
First, the 400 grit wet is too course for the final wet sanding
prior to
finish painting. After cure and shrink-back, you will be able
to see
400-grit sanding marks in the finish. 600-grit is the coarsest
grit you can
use without having any problems with seeing any marks. You can
use a little
400 wet to do some rapid cutting down of thick spots in the
primer, but you
need to finish it off with the 600.
On the primer/sealer:
PPG recommends that the DP-series epoxy products be used in two
ways:
DP is used as an epoxy primer/adhesion base right over the bare
substrate
before you start doing any body work/filling/fill priming. On
metal cars,
this provides a sealed surface to prevent any corrosion (fill
primer is
porous, so it does not seal the steel from moisture
penetration). On 'glass
cars, the epoxy prevents any topcoats/primers from reacting with
the
composite underlayers, and creates a stable surface to work off
of. You
then apply the fill-primer (K36 or equivalent) over the top of
the DP. You
must topcoat the DP within 48 hours, or the DP will "seal up"
and you will
not obtain adhesion. If you go past the 48-hour limit, you must
scuff-sand
the DP to break the surface prior to priming over the top of it.
Once you have primed and sanded the car using K36, and you have
guide-coated
it and final sanded with the 600 wet, PPG recommends that the DP
be reduced
as a sealer and shot over the K36 (I can FAX you the PPG
DP-series data
sheet where they define and describe this technique if you'd
like. Your
paint supplier should have the data sheet where it recommends
this
technique). Reduced 25% with DT reducer, the DP becomes a
paint/primer
sealer rather than a primer. This thin coat of epoxy seals up
the porous
K36, and provides an excellent adhesion base for the basecoat.
It also
keeps the basecoat from possibly reacting with anything
underneath, and it
covers up any sand-through spots in the K36. You do not need to
sand the DP
sealer as long as you shoot your basecoat/clearcoat within the
time "window"
for adhesion. However, I find that I like to go over the DP
lightly with a
little 600 wet or a ScotchBrite pad just enough to pull the dust
"nubbers"
out of it and to produce a perfect surface. DP does not sand
well, and will
plug up your sandpaper quickly, so just knock the dust out of it
and then
shoot your basecoat. If you let the DP sit for more than 48
hours, you need
to scuff the entire surface up with ScotchBrite prior to paint.
When wet
sanding prior to paint, use cold water: Use of hot water for
sanding or
rinsing tends to cure and "skim" the surface. Use of cold water
tends to
leave the exposed "pores" in the sealer open for maximum
adhesion.
I have shot several non-show quality cars where I have not
sealed the entire
car with DP prior to basecoat. I have used the DP reduced as a
sealer only
to touch up sand-through spots in the K36, and then shot
basecoat directly
over the K36. I have not had any problems with cars shot like
this. But
PPG recommends the sealer step method in all of their
literature.
Lars Grimsrud
Lars, I appreciate your help on this, and believe me, the hard and heavy question period is just beginning. In about another week, once I get the shop cleaned out and set up for paint and am ready, I'll be like a human question howlitzer. :D Be prepared. :cheers:
Oh yeah, is the 48 hour window the same on all layers, from sealer, to primer, to base to clear? I ask be cause work may interfere with this process a little. We'll have to see. Would I be able to spray all of it in a 2 day period?
[Modified by Dalannex, 1:33 PM 1/10/2002]
