PPG K38 Paint Help.........

[68mmcharger]

Currently spraying K38 on front fenders and trunk lid. Pot life listed is 3/4 - 1 hour at 70 degrees. Here in Florida, shop temperature is 90 degrees or so. At this temp pot life seems to be about 20 minutes. With a dry time of 10-15 minutes between coats, a full cleaning of the spray gun is required between each coat. WHAT A PAIN!!

PPG only list 4 to 1 mix ratio with no provisions for temp variations. Are there any other options for mixing/spraying this primer that anyone has used?  Any way to avoid cleaning of gun between coats?

Thanks.....Kevin

[hemi-hampton]

This may possibly help, Use half as much hardener &/or a Retarder to slow it down. I know when I had this Problem with a thick Sikkens primer the tech sheet said use half as much hardener. LEON.

[69 OUR/TEA]

Hi Kevin,first,if you are at 90 degrees,yes your pot life goes down,but also does your time between coats.From 10-15 minutes,it probably goes down to about 5,or just make sure you have flashed off before you apply the next coat.I use K38 occasionally,it's a good primer but prefer NCP 271 alot more.IMO,K38 drys fast anyway,so if you are at 90 degrees you will be recoating alot faster than 10-15 minutes.
   Second,if you noticed whatever primer you are spraying,if you have mixed up enough to do 4 coats,by the time you get to your 3rd coat it seems like the gun is spraying dry,it's because the primer is drying in the tip as it sits waiting for the next spray,Even if I have enough made to spray 4 coats,I still clean my gun after the second coat(even if I have to rush),so it sprays just like it did on the first 2,nice pattern and wet.Quite honestly,I try to only make enough for 2 coats,clean the mixing cup and make more later for the 3rd and 4rth.
   DO NOT become a chemist,whatever the tech sheet offers you for mixing ratios and products to use in it,that's what you do!!!The only other additions for K38 are DX84 Enhancer(to speed it up if you're in a cold environment)and DX814 Flexibalizer(name says it all).
    I have been using PPG for years with great results and have seen people alter from what tech sheet says,then blame the product when something fails .99% of the time when a paint product fails it is the users error.Bottom line,there is just to many hours in doing a paint job/resto,etc to be risking something going wrong,especially if you are a shop and have a call back because of it.If it boils down to cleaning the gun that frequently,so be it.

[Charger-Bodie]

Hi Kevin,first,if you are at 90 degrees,yes your pot life goes down,but also does your time between coats.From 10-15 minutes,it probably goes down to about 5,or just make sure you have flashed off before you apply the next coat.I use K38 occasionally,it's a good primer but prefer NCP 271 alot more.IMO,K38 drys fast anyway,so if you are at 90 degrees you will be recoating alot faster than 10-15 minutes.
   Second,if you noticed whatever primer you are spraying,if you have mixed up enough to do 4 coats,by the time you get to your 3rd coat it seems like the gun is spraying dry,it's because the primer is drying in the tip as it sits waiting for the next spray,Even if I have enough made to spray 4 coats,I still clean my gun after the second coat(even if I have to rush),so it sprays just like it did on the first 2,nice pattern and wet.Quite honestly,I try to only make enough for 2 coats,clean the mixing cup and make more later for the 3rd and 4rth.
   DO NOT become a chemist,whatever the tech sheet offers you for mixing ratios and products to use in it,that's what you do!!!The only other additions for K38 are DX84 Enhancer(to speed it up if you're in a cold environment)and DX814 Flexibalizer(name says it all).
    I have been using PPG for years with great results and have seen people alter from what tech sheet says,then blame the product when something fails .99% of the time when a paint product fails it is the users error.Bottom line,there is just to many hours in doing a paint job/resto,etc to be risking something going wrong,especially if you are a shop and have a call back because of it.If it boils down to cleaning the gun that frequently,so be it.

VERY well said !! 

[68mmcharger]

Thanks guys for the feed back. I had not considered that the dry time would go down as you said, very good point.

I am having trouble getting a single wet coat laid down. It's drying before I can get the first coat down.  I'm mixing 8-10 oz at a time. I'm sure I'm not the fastest painter but....

Attached is a picture of the paint booth set up.  Should this primer be smooth when dry? I'm ending up with a rough surface using a Ingersoll Rand HVLP gun with 1.4 tip. Gun says max pressure of 43 psi on handle. I am assuming that results in 10 psi at the cap. Gun literature says nothing. I have varied pressure from 25 to 40 with same result.

The epoxy primer laid down smooth but I did have some problems with the gun not feeding continuously. It would occasionally feed for 2 feet and skip 3 inches or so. I made sure cup vent was not clogged, air pressure is steady coming into gun based on gauge regulator connected at gun.

I know I'm throwing a lot of things in on this but maybe you guys have some ideas that will help.

Thanks....Kevin

[hemi-hampton]

I dont like HVLP's but not in California either. I'd suggest a non HVLP with bigger 2.0 tip/Fluid nozzle. I specifically bought a cheap $50 2.0 tip primer gun just for that occasion. Works for me. Dont care how it lays down, I'm going to block the hell out of it anyways. LEON.

[69 OUR/TEA]

Hey Kevin,you need to fix that problem with that gun or get a new one,you do not want dry spray or light spots varying like that.I use my Devilbiss GTI with a 1.5 tip and it works fine.K38 is designed to be sprayed with a 1.4-1.6 tip,it is to be no more than 2.5 mills dry per coat,not to debate with Leon,but a 2.0 tip to me is to large for a urethane primer,but more suitable for polyester primer where a 1.8-2.4 tip is needed.If you are dealing with a panel that is going to be needing alot of blocking ,repriming,blocking,repriming,you should switch to a polyester primer to get your high build,then once you get it straight where you want,go back to the urethane.
  Also a couple things  to keep in mind about K38 if you don't already know and is important,I see you primed the whole panel,if you do some blocking or more bodywork and need tp put more on,you must prime the whole panel.K38 cannot be spot primed over itself,it must be at least covered larger than the last area but in your case the whole panel.And K38 needs to have a finished sanded thickness of 2.0 mills or more for ahesion purposes,so if you break thru while sanding,you need to reprime the fender again.

[68mmcharger]

I'm at a loss as to what else to try with the gun. I guess I may have to replace it. Thanks for the info on spot priming. I saw that note in the tech sheet but 69 OUR/TEA's wording is clearer. Should K38 be smooth after spraying?

Thanks....Kevin

[69 OUR/TEA]

Hey Kevin,yes it should be smooth,smooth enough so if you wanted to sand with 320 grit.

[68mmcharger]

Thanks for all the help. I will keep you guys informed.

[hemi-hampton]

If you want it smooth then you dont want to go with my 2.0 tip. Better use a 1.4 for smoothness. Have fun. LEON.

[83CHARGER2.2]

Kevin,

I hsad the same problem!

Hemi hampton is correct in stating that yiu need to use a bigger tip.  you said that you hav e a HVLP gun, but did not say if it was a siphon or gravty feed.  A 2.0 tip in a gravity feed is not the same as a 2.0 tip in a siphon.  The siphon has to b bigger as the siphon action with the air needs a larger tip size for the compined spray.  The Gravity relies on gravty so the size of the tip is all liqud, no air.

Wehn temp goes up, the pot life gets shorter.  This is obvious, based on set temps.  Call the manufacturer tech line, (not the paint store) and have them explain to you that there is a product called extender.  (Just as the D84 was the accellerator).,  Extender allows the hardener not to harden quickly and slows pot life.  A retarder is used for slowing down dry time after it is sprayed on the pannel.  It would help with orange peeal and texture layout.  Thikn about it.  with high temps, the reducer that is built in the primer is dryed too quickly.  Therefore adding reducer will help the spray of the product, and will decrease the viscosity or thickness of the prodct.  This will both help you situation. 

Lastly, switch to another primer.  K38 is fast, or put extender or reudcer in it.  Try DPS3055 which is a slower product that my paint store recommended to me.

[hemi-hampton]

If you read the tech sheet for K36 it say's that adding reducer will double the pot life time. I assume reducing the K38 would provide the same benifits. The reason the tech sheet does not give that option on the K38 is because it is not intended to serve double duty as a optional sealer like the K36 does. Give this a try & see what happens, 4-1-1 with slow dry DT Reducer. Try it with & without a bigger tip & then decide which you like better. LEON.

[Charger-Bodie]

If you take only one thing from this thread ....let it be this: DO NOT BECOME A CHEMIST!!!! follow the product tech sheet to the T and you will not have trouble! A 2.0 tip is WAY too big for primer surfacer UNLESS its a siphon feed gun. If the K38 is sprayed correctly it will be very smooth................just remember they write the tech sheet for a reason! don't do things that are not outlined within the pages for the product you are using or you will probably end up with a mess in the long run. 

[hemi-hampton]

If he went exactly by the tech sheet then he would have to wait for a 70 degree day to prime. Heres what you do then. Call the Hot line for advice. LEON.

[Charger-Bodie]

If he went exactly by the tech sheet then he would have to wait for a 70 degree day to prime. Heres what you do then. Call the Hot line for advice. LEON.

Yes BUT the last thing a nivice (no offense) needs is advise telling him to alter a product. The tech line is good advise though!

[hemi-hampton]

I'll agree with you on going by the book & doing it right. If he was to talk to my buddy that runs the PPG Paint school here in Detroit (novi) he'd  straighten it out with some good advise. LEON.

[68mmcharger]

Good discussion, guys. My gun is a gravity feed one. By the tech line are you talking about this number: 1-800-647-6050? Will they answer questions to anyone who calls?

I guess switching to another primer might be an option. I bought 2 gallons of K38. Maybe the paint store would take the unopened one back. I still have a lot of the first gallon left. At $228 a gallon with catalyst it sure is expensive. I went with it since it is so highly praised by guys on here like Drop Top. Has anyone heard from him lately?

Kevin

[69 OUR/TEA]

If he went exactly by the tech sheet then he would have to wait for a 70 degree day to prime. Heres what you do then. Call the Hot line for advice. LEON.

It does not say to wait till 70 degrees to spray, it is telling you the spraying characteristics,pot life,and dry times to sand "AT" that temp.I have sprayed this primer at colder and hotter temps,I use my Devilbiss GTI w/1.5 tip,works great for me.Just like when you spray clear,depending on the temp,you may have to recoat sooner or later then what the tech sheet says.68mmcharger has yet to get a new gun and try that and tell us how it works.

[hemi-hampton]

Never said it said you had to spray at 70 degress, he said being 90 degrees it's drying to fast for him & tech sheet gives no options/ alternatives to slow down drying time. Ihot68 seems to be saying since no options on tech sheet nothing you can do to slow it down, only thing you can do is go by tech sheet.  All I know is I dont have this problem with my primer spraying. Seems everybody else in here has the answer for him so I'll stay out of this conversation from this point on. LATER.

[Charger-Bodie]

Never said it said you had to spray at 70 degress, he said being 90 degrees it's drying to fast for him & tech sheet gives no options/ alternatives to slow down drying time. Ihot68 seems to be saying since no options on tech sheet nothing you can do to slow it down, only thing you can do is go by tech sheet.  All I know is I dont have this problem with my primer spraying. Seems everybody else in here has the answer for him so I'll stay out of this conversation from this point on. LATER.

What I meant about staying with the tech sheet was about the the mixing of the primer. The temp should only change the way its sprayed!

If its hotter than 70 the flash times between coats will be less and if its cooler than 70 you will need to wait longer for it to flash between coats.

My main point is that you should never mix things into a product that arent on the tech sheet!! If it was widely accepted to add something to it the techs would have it listed in the sheet! When you are dealing with a chemical there are enough variables without throwing in some reducer or enhancer etc. into the mix too. 

[hemi-hampton]

Heres what one of my PPG Gun chart has to say. Some say a 1.8 tip to big but here it is in black & white from PPG themselves. All I know is that out of 25 years of spraying my rule of thumb is the thicker the material the bigger the tip. A .08 tip is good for super smooth atomization on certain products.

[69 OUR/TEA]

Don't want to ,but the chart says the 1.8 is for a larger fan for going faster and complete jobs.Pretty much I prime panels individually,maybe two at a time,thats just me.That chart shows the PRI gun as the gun for using the products metioned,K38 using a 1.6 tip.Drop down to where it shows sealers,as I said I have/use a GTI,cross over and it shows for the same jobs it uses a smaller tip,so the gun apparently atomizes differently than the PRI.It does not show reccomended tips for when using a GTI for their primers,but I still use it for priming,and as I had said I use mine with a 1.5(the gun came with 1.3,1.4,and a 1.5),no problems.One more note,as has been mentioned that since K36 offers a reducer that can be added by the tech sheet,and K38 does'nt,note on the chart showing the smallest tip for K36 is a 1.4 and the K38 being a 1.6(with the PRI gun).That is pretty much showing you that the two products are different and don't assume that because you can put reducer in K36,that you can do the same to K38.
  Anyway,as I said,I think the biggest problem that 68mmcharger is having is with his gun,and before he calls the primer the culpret,get a new gun,a name brand one from an autobody supllier,not from home depot.:FWIW,NCP271 is my primer of choice from the PPG lineup.Twocents:

[68mmcharger]

Sprayed some more K38 today. Tried taking the strainer below the paint cup out and gun worked much better. At least now I get a steady spray at risk of clogging spray cap. Had to narrow fan width down and move fairly slow to get a wet coat. Surface is a LOT smoother. My Ingersoll Rand gun came from a tractor store, not Home Depot. Does that make it better??

Temp was 82 in shop today. Primer sprayed better. At least I was able to get 10 ounces down without it drying in gun.

Will the PPG tech line guys talk to anyone that calls?

Kevin

[hemi-hampton]

You said yourself the 1.8 is for moving faster, If it is drying to fast & your moving to slow then you want to move faster. 


P.S. Charts back up what I been saying. 1.4 for k36 & 1.6+ for k38. Why, Because the k36 is thinner then k38 especially when reduced & used as a sealer. I thought all this was common knowledge & common sense.