For the last number of years, I've been working on a truck during the Winters for My Fiance's Father. I've been using the same Limco 800k primer the whole time. This year for some reason, I've had issues some of which I think can be attributed to my gun but, most I think are coming from the temp outside. Most of the time I've worked on the truck it has been cold although, the garage is heated.

The truck is almost done so; I've just been working away this year to wrap up the job. The temp has been in the 70's to 90's.

My issue is the primer is drying before I can even get it on the larger panels which is also clogging my gun.

The primer calls for 4:1 primer to hardener but, using this ratio, the primer is starting to dry and clump up in 5 minutes or less. I've tried using a little less hardener and have also thinned it out but, I'm still having issues with it drying too fast.

I've been cleaning my gun between coats and cleaning out my mixing cup before coats given how fast the stuff is drying but, I can't keep up.

I keep trying different things but, nothing seams to work. Given the primer needs a catalyst, I can't not use the hardener and worry about using less than what is called for.

I've never had an issue with any primer I've used over the years like this.

What else can I do?

I will guess a clogged fluid passage in the gun .

Gun details would be helpful, I normally reduce the 2K primer to my liking and equipment, to suit.

a quick google search on your primer tells me there re 2 different catalysts for it,810 and 820. i would assume different catalysts for different temps. my guess would be get the WARM temp catalyst and you should be fine.
i would recommend keeping it out of the sun when using it also.


on another note if the catalyst is old that could be your problem also. technically speaking after a catalyst is opened more than 30 days. it's not 100% viable anymore and can create problems with cure.

What size tip are you using in you gun to spray with?

Thanks for the replies.

I used a different gun today and had the same issue. I had a small spot to prime that I had to fan out a little bit each coat. By the third coat, the primer was drying in the gun. From the time I mixed the primer to the time it was drying in the gun, only 10 or so minutes past. If I were spraying a larger section, that would not even allow enough time for the coats to flash.

I did look at the two different types of catalysts but, there was not too much information on the difference. The spec sheets on them do indicate that the cure time is longer for the 820 catalyst so; my assumption would be that it would dry slower between coats than the 810 that I've been using.

The gun I used this morning has a 1.3 tip which is on the small side but, I borrowed it from a friend to do one small spot that I wanted to get done. My gun that I've used for the last 15 years has a 1.5 tip.

I ordered a new gun last night; I'm tired of messing with the other one but, I do think the issues I've had are a result of the primer drying too quickly.

I have just the back of the cab to get done so; I just want to get done with it. I think I'm just going to clean the gun between coats and mix the primer for each coat.

A lot of primer guns are (off the top of my head) 1.8 but never heard of primer drying in the gun in 10 minutes.

HOW OLD IS THE PRIMER AND CATALYST.
i don't care what you have done in the past. you have never had this problem in the past so what happened in the past doesn't matter now.


the data sheet says pot life in 1.5 hours, not 5 min, so something is wrong with the product or the temp you are using it in is to high for the catalyst. i know PPG K36 primer the heat can kick it to jell fast also. you might have to spray in lower temps to get it to work.

if the heat is causing the product to gel you don't need to wait 5 min between coats. re-coat immediately after flash off.
or you could add a little retarder to slow it down some.
or use the slower catalyst, the extended cure times of the other catalyst is longer is because it is designed to be used in higher temps.

the gun tip size shouldn't make a lot of difference. the data sheet says 1.5-1.7 tip. if the tip is to small it will just spray really dry.

https://www.coatingsmall.com/cap_data_do...LH810_LH820.pdf

Are you sure you are at 4:1 on the primer to hardner mix?
How did you measure it. Eye ball it or use a mixing cup?
From the sound of it you might have put in a little more hardner in the mix.
I had the same problem a few months ago , using 2 K primer. I eyeballed the amount hardner and I was off on the ratio , causing the mix to harden sooner. Got a paint mixing cup, measured exactly 4:1 proportion and it hardened much slower on the 2nd go around. I also added a little reducer for better flowout. Everything came out great the 2nd time.
By the way, I used a medium temp hardner.

I've seen 2k primer that has been stored in less than ideal conditions {too hot,too cold} gel up to the consistency of cottage cheese within a few minutes after combining the ingredients..

We got the primer and hardener within the last month or so.

I've been using a mixing cup to measure the ratio. The spec sheet calls for 4:1. I have gone a little light on the hardener and it has made no difference. I went real light this past weekend and it still made no difference.

We ordered some of the 820 hardener and confirmed that it does in fact dry slower between coats. Hopefully between that and the new gun, I should be able to lay some primer out this weekend like normal.

Hopefully I can block and prime it one last time and I'll be good to go but, two more times may be needed to get it as straight as I want it. I have two spots that are a little weird/low.

I can't wait to be released from my body work bondage. 3 Winters and more of working on this thing for nothing more than Lunch the days I work on it. I'm retired after this; people can pay/learn to work on their own stuff.

I'm done; everything worked out great today.

I used the new 820 hardener and we got some new primer. We had enough of the old primer left but, I figured it could have been older than what we thought (maybe sitting on the shelf for awhile before we got it) so; to be safe, I opened the new stuff.

The new gun sprayed awesome and I was able to prime like I normally do.

Who knows what the exact issue was but, I really think it was the hardener just not liking the warmer weather.

I'll clean the old gun up. At least I have two guns now and they are almost identical which will be nice if I ever use both to spray base clear or something like that.

you are probably correct on the hardener and temps. i think that was my second suggestion after old products shelf life.

with urethane products technically the catalyst is bad 30 days after it's opened.

old products can react in unusual ways. i have used 5 year old products without problems and used 30 day old ones and had problems. urethane products can react to high temps and humidity so proper solvents for the temp it's used in is important. sometimes the primer solvent or hardener solvents evaporate while sitting on the shelf if the lid isn't put on properly. if enough solvents evaporate you can over catalyze without knowing it.