 motthollow
"3rd Year" Silver Supporting Member
Posts: 191
Loc: North Jersey
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03-17-12 08:07 PM - Post#2203980
I just used a HVLP gun for the first time and my two coats of DP40 are less than perfect which is OK because I have to apply filler on low areas anyhow (welded in lots of unnecessary holes in my firewall). If I apply body filler within the 7 day window I'm afraid when I sand both the body filler (Evercoat Glaze) and epoxy primer, the DP40 will become "gummy." Or should I wait for the DP40 to become rock hard (will it ever??), so it will sand easier when I apply the filler? Thanks for your opinions. 
"None of my cars will ever be finished... just that some are further along than others."
'56 Sedan Delivery, '55 half-ton p/u, '42 GMC p/u,'38 Chevy, more waiting! www.picturetrail.com/motthollow |
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 MPandC
"8th Year" Gold Supporting Member
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03-17-12 09:16 PM - Post#2204014
In response to motthollow
I haven't used the PPG epoxy myself, but from what I've heard /read on the subject, when using PPG's epoxy, you would need to apply anything on top of the epoxy within the recoat window. If it fully cures, it will require scuffing and a reshoot of epoxy, then then next layer (high build?). Apparently it does not have good mechanical adhesion with other paints after curing, hence the recoat with the same epoxy. Most will shoot the epoxy, let it flash for an hour or so, then apply a high build that is more friendly to other paint applications.
Disclaimer: Subject to correction by those who use it...
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 Vista Cruiser
Moderator
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03-17-12 09:20 PM - Post#2204016
In response to motthollow
I would wait a few days at least, and then scuff it before you apply filler. That will give you mechanical etch, or scratch for the filler to bite.
I never thought of an epoxy window to apply to filler, but to top coats of paint.
The epoxy subject is always a good one here, no two opinions the same. 
Kenney AKA Blizzardboy
09 Impala SS....82 T/A.........72 Vista Cruiser
12 Cruze....98 Riviera...07 C-1500
68 Firebird
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motthollow
"3rd Year" Silver Supporting Member
Posts: 191
Loc: North Jersey
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03-18-12 04:02 AM - Post#2204067
In response to Vista Cruiser
Whoops, the filler is Evercoat Rage Gold... not Glaze, which is what my brain was thinking last night at midnight.  Scuffing won't be an option; I need to sand it because dummy that I am the P sheet said 8-10 psi at the cap, so I set my air pressure at the gun at... you guessed it. I had good coverage but the finish is very rough. I now realize the inlet pressure should have been between 28-30 psi. So I need to either sand it smoother or apply a skim coat of Rage over the entire surface which would build up the thickness.
"None of my cars will ever be finished... just that some are further along than others."
'56 Sedan Delivery, '55 half-ton p/u, '42 GMC p/u,'38 Chevy, more waiting! www.picturetrail.com/motthollow |
Edited by motthollow on 03-18-12 04:21 AM. Reason for edit: No reason given.
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brad_bb
Valued Contributor
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03-19-12 07:40 AM - Post#2204566
In response to motthollow
There are two catalysts for DPLF epoxy. Use the fast one - DP402LF. The slow one will remain pretty gummy and is not useful for the stuff we do(where we may have to leave the project for weeks or more before we get back to it). Which catalyst did you use? Doing filler work, I often don't apply filler within the window. This is because I may prep and seal many parts all at once and by the time I get to bodyworking them, it may be some time later, even years sometimes. Just scuff the epoxy after it has cured with a red scotchbrite pad or a fine grit paper, and apply your filler.
Here I found a P-sheet online:
DPLF P-sheet
| If someone else can design it, I sure as heck can figure out how to fix it! |
Edited by brad_bb on 03-19-12 07:43 AM. Reason for edit: No reason given.
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 Rick_L
Honored Member
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Loc: Katy, Tx, USA
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03-19-12 06:06 PM - Post#2204782
In response to brad_bb
The p sheet does not mention scuffing for filler.
The way I read it is that you can apply filler, primer, or paint within the "window". Outside the window, you scuff and respray the epoxy primer.
I know a lot of guys don't do it this way, but that's what they say.
They are telling you there's a chemical bond with the DPLF if applied within the window.
What's unmentioned on the p sheet is the quality of the mechanical bond if scuffed or sanded.
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brad_bb
Valued Contributor
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Loc: Joliet, IL.
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03-19-12 07:22 PM - Post#2204818
In response to Rick_L
I never get the opportunity to apply filler within the window. By the time I prep the bare metal parts to seal, and get them sealed, that's usually it for the day. In a collision shop environment I can see them applying filler within the window. But I'm hobby restoration, not collision. Oustide the window, scuff(and wipe/blow gun), and apply filler is the way I've done it for 20 years.
| If someone else can design it, I sure as heck can figure out how to fix it! |
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wagonman100
Super Senior Member
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Loc: Baltimore, MD
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03-19-12 08:33 PM - Post#2204862
In response to brad_bb
I work in a collision environment and epoxy primer is rarely used in production body shops. At my shop we use etch prime on bare metal and a 2K high build as a primer. We also apply body filler to bare metal.
I don't have any experience with epoxy, but depending on how rough the epoxy is, I would do it this way... I would scuff the epoxy when it is dry and apply a high build primer over it and then do the filler work (also after scuffing the dry high build). That way the high build can fill the rough epoxy and when you sand the filler, you'll be sanding the high build and not the epoxy.
Again, as Robert said, this is subject to correction by someone who actually uses epoxy on a regular basis.
Jay
Some days it's not worth chewing through the restraints.
1999 Silverado Z71 4X4 extra-cab short bed
1983 Malibu Fauxmad - tubbed
1978 El Camino Kustomized
1972 Monte Carlo
1957 210 handyman wagon
1957 Nomad sport wagon |
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motthollow
"3rd Year" Silver Supporting Member
Posts: 191
Loc: North Jersey
Reg: 01-27-10
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03-20-12 04:21 AM - Post#2204931
In response to wagonman100
Thanks all for your replies. I waited 3 days (the recoat window is 7) and filled the leftover depressions from welding and grinding with Rage. It might be my eyes (at age 67) but the epoxy seemed to smooth out a little bit during this 3 day time period. I was worried because this was my first with a HVLP gun and also heard about the filler becoming gummy. Yes, I used the faster acting catalyst and everything seems to be going real good. Today I'm shooting the final coat of DP40 (with the right nozzle at the right inlet pressure), then will follow with 3 coats of 2K primer/surfacer... allowing at least a week for each coat to harden, then applying a seal coat before my base coats and clear. I'm following Larry Lyles book. He is very thorough and clear in his explanations procedures, dry times, etc. I also have the P-sheets which got me into trouble in the first place when it mentioned 8-10 lb. of air as I said in my intro post. Thanks again. I updated some photos on my PT website. 
"None of my cars will ever be finished... just that some are further along than others."
'56 Sedan Delivery, '55 half-ton p/u, '42 GMC p/u,'38 Chevy, more waiting! www.picturetrail.com/motthollow |
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wagonman100
Super Senior Member
Posts: 12952
Loc: Baltimore, MD
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03-20-12 04:43 AM - Post#2204934
In response to motthollow
It probably did flatten out a bit. As it dries, it shrinks. That is one reason to let things set for a while before going to paint. It gves the materials time to shrink and reveal any imperfections that may arise from that.
In the production collision world, we don't have time for that unfortunately. I am always very careful about it and use 220 as my final grit before high build primer. But I noticed on my wife's car that I can see a few sanding scratches here and there from a repair I did three years ago when the car got totalled for the second time. We didn't own it the first time and the second accident wasn't her fault, just to clarify.
Jay
Some days it's not worth chewing through the restraints.
1999 Silverado Z71 4X4 extra-cab short bed
1983 Malibu Fauxmad - tubbed
1978 El Camino Kustomized
1972 Monte Carlo
1957 210 handyman wagon
1957 Nomad sport wagon |
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brad_bb
Valued Contributor
Posts: 4190
Loc: Joliet, IL.
Reg: 07-13-01
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03-21-12 07:49 PM - Post#2205885
In response to wagonman100
I'll also add to what I said, that more often than not, I apply filler to bare metal. What I'll often do I seal the part or panel in DPLF sealer, then when I go to do filler work, I'll end up sanding off a good bit of the sealer. Also, I'm assuming that you applied filler a number of times and sanded it out til you were happy with it. I would then go strait to a high build urethane primer, block that out til I'm happy, then when all is done, seal it all in DPLF. Then paint, or if outside the window(typical) scuff, wipe down, blow off and paint.
| If someone else can design it, I sure as heck can figure out how to fix it! |
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motthollow
"3rd Year" Silver Supporting Member
Posts: 191
Loc: North Jersey
Reg: 01-27-10
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03-22-12 08:27 PM - Post#2206318
In response to brad_bb
Thanks for the updates. I followed Larry Lyles book and did the following: 2 coats DP40 using the faster catylist, waited a couple days and filled the depressions etc., shot another coat of DP40 over everything, waited 2 days until today and shot 3 coats of D8005 primer/surfacer, waiting 5-10 minutes between coats. It looks great. I am going to wait a couple weeks and then block sand and continue with my base and clear. Why 2 weeks? That's what he recommends for the VOCs to outgas or something like that (That's what I do a lot of these days also!). Like he says... this is a hobby, not a production shop. Besides I just brought home a 55 2nd series p/u that I can play with. I'm going to try to post some photos. If they don't come up, they'll be on my website.<a href="http://www.picturetrail.com/gallery/view?p=10& ;imgid=401737663" target="_blank"><im g src="http://pic80.picturetrail.com:80/VOL1925/13134821/2 3919602/t-401737663.jpg" border="0" alt="Free Image Hosting at www.picturetrail.com"/></a>
The photo didn't come up... just a bunch of numbers and symbols. I'll try again next week when I have more time.
"None of my cars will ever be finished... just that some are further along than others."
'56 Sedan Delivery, '55 half-ton p/u, '42 GMC p/u,'38 Chevy, more waiting! www.picturetrail.com/motthollow |
Edited by motthollow on 03-22-12 08:40 PM. Reason for edit: Photo didn't appear... just jibberish
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Vaughn
"11th Year" Gold Supporting Member
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03-26-12 09:56 AM - Post#2207664
In response to motthollow
A lot of people assume that epoxy needs to "air dry", but this is not really the case. The 2 components react chemically with each other, forming a rock hard surface. It has no "solvent" that needs to dry out of the paint (well, it has a solvent to allow it to be sprayed out of the gun, but once it evaporates the surface can be sprayed over). The two chemicals do not need "air" to cure, they can cure in a vacuum when combined.
The seven day window is when the 2 components on the surface is finally cured, but the solvent is basically gone after 24-48 hours. If you shoot within that seven day window, you won't have to scuff up the surface (as much) as if you do it later, when the surface is rock hard.
Epoxy primers are usually for guys that are working on a project at home. In a production shop - as Jay said - time is of the essence, and self etching primer dries quicker, so they can shoot the paint quicker. Epoxy primer is excellent at providing a "sealed" coat above the metal, so that the guy in his garage can take care of all rust repair once and be done with it - until he gets the money/time to shoot the final paint. It is also an excellent paint sealer - isolating the base paint from whatever paint the guy finally chooses - so that the old paint and new paint don't chemically react with each other.
Epoxy primer is a base coat, BUT IS NOT THE FINAL PRIMER, and was never intended to be. Epoxy doesn't lay down well, so should really not be used as the "final" primer underneath paint - unless you are shooting a tractor or something, and just want it to look good from 20 feet away. Epoxy primers are also EXTREMELY DIFFICULT to sand, which makes them bad for a final primer, which needs to sand smoothly. This is what 2K high build primers are for. A 2k primer is there to spray out smoothly and fill small dents/pinholes (basically bondo in spray form), and to provide for a surface that can be sanded out easily and exceptionally smoothly. This is to provide a flat surface underneath the paint (ie without the orange peel surface of an epoxy primer) so that the paint and clear will lay flat - minimizing the amount of wet sanding, cutting and buffing for that "glass smooth look".
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 linus7226
Gold Supporting Member
Posts: 60
Loc: Huffman, Texas
Reg: 03-13-09
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07-17-12 10:09 AM - Post#2249085
In response to motthollow
I just used an HVLP gun for the first time too. Actually I just used a paint gun for the first time! I am also using DP40 and I did not think the finish was as smooth as it should be. It has a bit of an orange peel look. Not real rough but not really smooth either. Can you walk me thru the pressure settings. I guess I did the same thing you did. I have a pressure guage at the gun and I set it to 10psi with the trigger depressed. I take it from your post that does not give you 10psi at the nozzle? I don't understand the inlet pressure vs. nozzle pressure.
1956 Chevy 210 2 Door Post
1946 Chevy Stylemaster 2 Door Sedan |
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Vaughn
"11th Year" Gold Supporting Member
Posts: 13560
Loc: Colorado Springs, CO
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07-18-12 12:00 PM - Post#2249544
In response to linus7226
DPLF 40-90 epoxy primers will always form a surface that looks like it has orange peel - it will have it more or less, depending on your spray experience, your gun and how much thinner you use.
This is why you would want to use a 2K primer over it, so that you can sand the 2K smooth before painting. 2K is designed to be sanded, and will provide a very smooth surface after sanding so that the final paint looks flat. DP 40's purpose is to provide a rock hard/difficult-to-remove primer base - it is not intended as a final primer before paint. DP 40 was never intended to sand well, or to even be smooth coming out of the gun.
The 10 psi listed on the gun is the inlet pressure, or the pressure at the gun regulator. A lot of people assume that it is the cap pressure, but it is not. Think about it this way - how would you be able to measure the pressure at the cap, so that you could set the gun to that pressure?
Gun manufacturers know this - so they calculate the pressure drop through the gun, then come up with a pressure that the gun inlet needs in order to spray material with the minimum overspray while still maintaining the proper spray pattern for the best coverage.
When I started using HVLP guns, I asked several gun manufacturers whether it was the cap pressure or the gun inlet pressure - and the above explanation is what I was told. It is the gun inlet pressure.
That pressure is the starting point - not the final "perfect" pressure that you should set the gun to. Materials have different viscosities and different tip size requirements. So, you should play a bit with the setting to get your perfect spray pattern with minimum overspray.
Most people shoot primers with their 1.3 tip HVLP gun, which usually doesn't work as well as it should. Since primer (especially epoxy primer) has a high viscosity, the HVLP gun with a small tip is going to have trouble spraying that thick primer through the gun - so most people turn up the gun inlet pressure in order to spray it. If you are limited to only that tip size, you are going to have to thin it quite a bit to reduce orange peel, so you don't get as much coverage, and there is a greater tendency for runs (especially in people with limited spray experience).
Orange peel itself - is an inability of the paint or primer to self level or flow outwards so that it seeks it's own level. Therefore it looks "lumpy" or resembles an orange peel. This is also why adding thinner to it reduces orange peel, because thinner allows the materiel to flow outwards - but like I said, it also greatly increases its tendency for runs.
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Rick_L
Honored Member
Posts: 24741
Loc: Katy, Tx, USA
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07-18-12 03:32 PM - Post#2249608
In response to Vaughn
"The 10 psi listed on the gun is the inlet pressure, or the pressure at the gun regulator. A lot of people assume that it is the cap pressure, but it is not. Think about it this way - how would you be able to measure the pressure at the cap, so that you could set the gun to that pressure?
Gun manufacturers know this - so they calculate the pressure drop through the gun, then come up with a pressure that the gun inlet needs in order to spray material with the minimum overspray while still maintaining the proper spray pattern for the best coverage."
The above is incorrect except for the general idea that pressure at the inlet and pressure at the cap are different. To be classified as an HVLP spray gun, the cap pressure must be 10 psi or less. And 10 psi cap pressure is where they are designed to work, and to meet regulations.
You are correct in that with most guns there is no way of measuring the pressure at the cap. The few that do have a cap for actual spraying and another cap for measuring the pressure at the cap. That special cap will have a fitting with an internal probe placed where the pressure is to be measured. A pressure gauge is connected to the fitting. Obviously you can't spray with this setup - all those things are in the way.
What spray gun manufacturers do is tell you in the operating manual what pressure at the gun inlet produces 10 psi at the cap. This will vary from gun to gun. I have a gun that needs 23 psi at the inlet and another that needs 50 psi at the inlet, both for 10 psi at the cap.
Certainly 10 psi at the inlet won't produce 10 psi at the cap. The internal workings of the gun will always drop the pressure.
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Nomader What?
Senior Member
Posts: 291
Loc: Bulverde, Texas, USA
Reg: 04-30-02
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07-20-12 01:26 PM - Post#2250300
In response to Rick_L
If you use epoxy primer and it sits for more than the recommended time(7 days), if you go over it with a scotch brite pad to scuff it, can you shoot your primer surfacer over it then or do you need to shoot on some more epoxy and then spray the primer surfacer primer right after that?
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Rick_L
Honored Member
Posts: 24741
Loc: Katy, Tx, USA
Reg: 07-06-00
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07-20-12 04:22 PM - Post#2250359
In response to Nomader What?
The PPG p-sheet says to scuff and re-shoot another coat of epoxy. I don't know about others.
A lot of guys don't do that.
Here's the way I look at it - if you shoot primer surfacer or top coat over the epoxy within the time window, you get the chemical bond between layers that was forumulated.
If you scuff it with too fine a grit, you may not get a good mechanical bond either. If you scuff it with too coarse a grit, you might sand through.
Decisions, decisions.
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Vista Cruiser
Moderator
Posts: 4439
Age: 44
Loc: Erie Canal
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07-20-12 06:37 PM - Post#2250419
In response to Rick_L
A lot of good advise.
I always had a better final finish if the epoxy has dried awhile to sand it with 320-600 grit on a 6 inch da, Velcro paper with an interface pad.
Then move onto primer, more epoxy, or top.
I was never one to watch the calender either. Clock, yes. Never trusted chemical bond of DP/DPLF past 24 hours. Always sanded/scuffed it after 24. JMHO.
Kenney AKA Blizzardboy
09 Impala SS....82 T/A.........72 Vista Cruiser
12 Cruze....98 Riviera...07 C-1500
68 Firebird
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