Problems with Die back

[Gbfan10G]

I'm having problems with die back. I have been having this problem for the last year or two, on about 5 separate paint jobs. I have tried so many things to resolve this and I am still at a loss. Barry has been awesome with suggestions on how to fix this, but I thought I would start a thread to keep it all in one spot

It seems to have started coincidentally when I purchased an Iwatta LPH-400 1.4

I have tried different base coats (Nothing high end, Shopline plus, Omni)

The last base I sprayed was a silver metallic, I waited over night to spray the clear. It looked great at first, no runs, shiny, looked like glass. AS the clear dried the next day, the die back showed up again like I get every time.

For my compressor, I am using a Sanborn 60 gallon compressor. When I started getting this issue, I thought it was water vapor. I have since created an after cooler with water trap between the pump and the tank. THis cools the air temp down considerably. I also ran 1/2 iron pipe about 20 feet down the wall to another filter. I also used a brand new 25 foot rubber hose with high flow fittings. I have tried various gun settings and air pressure and all have the same results.

At this point the only thing that as remained static is my air compressor, and the spray gun. I am out of ideas.

I sprayed clear on a paint can (I saw the recommendation on this forum. I will attach that pic as well.

 

[DATEC]

What clear you using?

 

[DATEC]

More info is needed like what clear?, what primer? How long you waited between primer and baseing?, where would it puke, where the primered area was?, where the base was applied only? if you bended the panel, would the area with no base (just clear) puke? or just the area where there was base applied? How about temp during and after?

 

[Gbfan10G]

Sure,
I'm using production clear. I've sprayed the base over SPI epoxy, I have also sprayed the base over a factory clear coat with the same results. (Scuffed with 400) That was the last attempt, when I sprayed silver metallic. (Also I waited overnight between base and clear)


I haven't really blended a panel, I have been painting doors, fenders, things like that. I tried some other SPI clear my dad had and it has done the same thing.

My base coats looked good and so did the clear, until it starts to dry.

 

[Chris_Hamilton]

This is all just a shot in the dark without knowing exactly what you did and how you sprayed it. First question did the (stored) clear ever get below freezing? If clear freezes it can cause issues. Is it die back (loss of gloss after it starts to cure) or shrinkage? Was the base reduced correctly? Was the sealer reduced correctly? Are you activating the clear correctly?
From the pictures the clear and the base looked like they were applied rather heavy. Are you allowing enough time between coats? (flash off) Low end basecoats can also be a factor in this as well. If I had to guess I would say you are shooting too wet (heavy) a coat without enough flash time between coats. Solvent gets trapped and even with overnight dry it still is trapped when you spray clear. What temperatures was all of this done in? I see you are from Minnesota so I know it's cold there. Spraying in too cold an environment will cause issues like you are experiencing.
More info please before one of us can help you.

 

[DATEC]

Temperature is a big issue. If the panel is cold but air temp is warm you can have an issue. If everything is good temp. wise during your painting/priming then gets cold when you leave that can cause issues. What temp reducer/hardner you use can be in issue.

There are alot of variables that need to be answered to give a good idea of what the root problem is. So if you can give a complete play by play including temps before during and after.

 

[Gbfan10G]

The recent base coat I sprayed the shop was a little cold, about 60 degrees. The green base I sprayed was in the summer and it was around 70 degrees out. (One of the blue pics was from last summer too)
I am mixing everything with paint cups, so I should have the ratios correct. The clear shouldn't have froze as I keep the shop about 40 and above all year. When I recently sprayed the base coats, I waited 15-20 min between 3 coats, and then overnight before the clear.

 

[elwood]

Is the correct temp reducer being used? If you don't have a laser thermometer it could help alot. Sometimes surface temp and air temp completely different. All advice given before is great info. Usually loss of gloss is from solvents escaping as everything dries. It could be a combination of things also. I normally write down everything so if something goes wrong I can look back to see if I can find out what I did wrong. Hope this helps.

 

[AAE]

I recall Barry saying that if product is kept below 50 it could have adverse effects on it's quality. Do you know what the temperature of the clear was when you applied? It takes about a day for it to reach a good sprayable temp when it's been kept colder. Just some thoughts.

 

[texasking]

Did the cans with clear only die back? The only time I've seen die back is solvent trapped or lower line base and clear. From the pictures it looks like base was sprayed heavy with very low pressure. Spraying base (or anything else) too wet with a fast reducer will cause solvent to be trapped and cause problems, also. Sometimes 15 or 20 minutes between coats is not long enough when temps are low. I recently sprayed with temps in low 50's and base was not dry enough to tack rag after 20 min. Sounds like you tried to do everything right but sometimes chemicals have a way of showing you who's boss!

 

[Barry]

Rather simple, now with this said I'm only speaking for my clear.
If mixed right.
If proper activator for temp is used.
Than clear can only die back by itself IF.
Both fan is run too long or over-baked and with these the clear will die back within no longer than 2 hours, usually in 60 minutes.
Any time the clear dies the next day or 2 days or longer it is 99.9% of the time solvents trapped in base.
Your using a low grade base that is way slower to dry than the good bases and will see the problem most with Black, Dk Blues and Dk Greens.
If silver does it, this is not normal as silver is a faster drying color.
Look at proper grade reducer or up grade reducer.
Look at longer base flash times.
Look at buying a better base.
Gun had nothing to do with it.

 

[Barry]

In picture these are empty drums stored in breezeway when we get 330 they pick up.
I painted color chip wed it was 50 out
And put 2 coats base with 870 med reducer waited 10 mins before universal and one wet coat.
No dieback on the overspray or the
On the color chips. This is abuse at its best but my bases are more in line with spies, standox or debeers.
Reducer might be first change and first coat of base i let flash longer, overnight does not help solvents trapped in first coat of base.

 

[bmenard]

Im here to tell you if you use spi slow reducer in that base, and wait 30 minutes between coats then overnight to clear this will not happen. I refuse to use anything but slow in base even on a one panel collision job. Slow is faster!

 

['68 Coronet R/T]

What is your compressor CFM output?
Do you have a water trap, regulator and particulate filter in line.
How are you setting your spray gun up?

The LPH400 has been a go to clear gun for a lot of years.

 

[Gbfan10G]

Im here to tell you if you use spi slow reducer in that base, and wait 30 minutes between coats then overnight to clear this will not happen. I refuse to use anything but slow in base even on a one panel collision job. Slow is faster!

On my last base, I switched the Omni Medium and used SPI Medium reducer with the same results. (This was a test Barry wanted me to try) I did give it overnight to dry.

 

[Gbfan10G]

What is your compressor CFM output?
Do you have a water trap, regulator and particulate filter in line.
How are you setting your spray gun up?

The last 2 times I set the gun up as follows
For clear
top knob2 turns out
bottom knob/fluid 2.5 turns out
psi29psi

I also tried

Top 1.5 out
Fluid out until trigger just hit
29PSI

For base I tried a lower pressure (this last time)
15psi
Top 2.5
bottom 1.5




The LPH400 has been a go to clear gun for a lot of years.

the specs are;

• 155 max PSI
• 13.4 CFM at 40 PSI
• 11.5 CFM at 90 PSI
• 240V

I have invested a lot of time into making sure the air is moisture free. I have an aftercooler installed between pump and tank, an automatic trap right after the aftercooler. Then 15-20 feet of iron pipe across the wall going into another filter/trap and a small inline desicant. It then runs to a 25 foot air hose and right to the gun with HF fittings.


At one point (several months ago)this compressor ran for hours straight when a line blew up. The shop was filled with smoke and I had to install a new valve plate assembly.

 

['68 Coronet R/T]

I don't know how others do it but here's what I have done to set that gun up.
Back fluid knob out all the way. Pull and hold trigger and then turn fluid knob in until you start to feel the trigger lift. Let off the trigger and turn the fluid knob in 1/2 turn more. This will put it about 3-3.5 turns out.

Attach your air hose and pull trigger full open and adjust the PSI at the gun to 22-24 (base) or 26-27 for clear.

Using masking paper taped to a wall, I put paint in the gun and open the fluid knob all the way out. Point at the paper keeping gun 4-6" from surface and squeeze the trigger to check the fan pattern and adjust to desired shape. Recheck psi at gun with trigger pulled full open after each adjustment.

Once the fan pattern is where you want it, point the gun and squeeze the trigger for 1 full second. Inspect the droplets in the pattern. They should be very fine and consistent in size with no signs of running. Keep your psi at the gun consistent but turn the fluid knob in 1/2 turn at a time until you have the desired droplet size.

This should get you real close. After I get the gun dialed in, I leave the settings alone and adjust the psi at the gun for the material I am spraying.

Let me add that when a spray gun is set right it has a certain sound to it. Once you get used to that sound you can pretty well dial them in by ear.

 

[Jim C]

to generalize this whole issue.....dieback/shrinkage is due to the primer/sealer/base/clear being put down and after it has cured the solvents are coming out of the paint film. if you allow all the solvent to come out of each paint step before moving on to the next then the shrinking will be minimal or not at all....assuming your using quality products. at some point you need to look back at your process, flash time and temps to see where this can be happening. the most common cause is not allowing the sealer and base process to flash long enough before applying the clear. base can feel dry and still be loaded with slow tail solvents. at room temp it can take 24 hours for base to completely dry. the lower the temps, the heavier the coats the more prone you will be to trapped solvents.

 

[Gbfan10G]

I think I am going to take my old door and test spray base and clear at different times and see if I have better luck.

 

[shine]

omni sucks. by the time you get coverage you've got too much mill build . crap takes forever to cure out and thats in summer. shopline aint much better. there's a reason it's cheap .