What happened?

C

Chris Martin

Promoted Users
Today I went to spray a couple small parts with the white epoxy primer I have (I think I bought it around December, stored inside the house at 70ish). When I started spraying I noticed some specs but then cleared out and sprayed fine.

When I went to clean the gun, it was full of semi-cured stringy sticky goo. Took me an hour to clean a touchup gun since the stuff would not dissolve with thinner. What a mess. The only thing that helped clean the gun was acetone (still would not dissolve it, just breakup in hundreds of solid specs).

The temperature in my shop was 74, parts and primer, hardener and reducer at same temperature since stored inside the house. I mixed the epoxy and let it sit around 5 minutes. Not more than 10-15 minutes in the gun before cleaning. Outside temperature around the same 74.

The only thing I can mention is that I sprayed 2K Regular the day before. Disassembled and thoroughly cleaned the gun yesterday.

What do you guys think happened? I sprayed my whole project with this primer and had never seen this happen. Can it be getting old? Looks good to me (primer looks bright white, mixes good, hardener is straw color and clear as always).

Mixed it 1:1 + 10% Medium Reducer.

Chris
 
I just sprayed SPI epoxy and activator dated 2019 and had no issues whatsoever. I put the caps and lids on all my stuff as soon as I pour it.

My guess is the gun still had some 2k primer in it.

When cleaning, I remove the cap and tip from my guns and soak them in clean lacquer thinner. I then brush them with a fine soft bristled brush and visually inspect that the holes are clear.
The same goes for the inside of the gun where the tip assembles. Once assembled I do a final rinse with reducer and pull the trigger to let it flow out into a cup.
 
I think I do a pretty good job cleaning the gun. I do take it all appart every time, rinse, brush, rinse, etc. I also use the stuff in the spray can to clean the orifices. I didn't strain. But the primer was bonded against the surfaces of the gun and cup so wasn't stuff that came when I filled the gun. The stuff didn't clean with thinner. I wonder if there was any residue that was still chemically active from the 2K that reacted with the epoxy primer. I have to say that for my entire project I used two different guns for epoxy and 2k so no contamination. Since this was small parts I used my touch up gun which BTW worked well despite the small orifice. Luckily the parts came out fine and it seems the primer is curing properly.
 
Rookie here but the only time I've had anything g close to that happen was when I mixed evercoat polyester primer in a cup that had dried clear from the day before stuck to the side of it. Just a thin film. And it resulted in a big mess that needed cleaning immediately before the poly dried up.
 
There was a stringy ball inside the gun's cup. Maybe an inch long. The walls of the cup had a sticky residue that wouldn't dissolve. Really strange. I wish I had taken a picture. At the end I didn't lose the job and I'm glad for that. But spending an hour to clean a little touch up gun was not fun. But no harm done at the end. Interestingly it seems the stuff was mostly on the walls of the cup and gun and on that big rats nest of a ball since no particles messed up the spraying. The stuff I painted was perfectly clean and smooth. Now, wait, I just remembered I left the gun in the sun for a couple of minutes while I prepped the parts (I sprayed outside). Poly cup. Very bright sun. UV?
 
I hate to say this, but I am pretty sure you've done something terribly wrong. I've been shooting SPI epoxy for close to 15 years now, and I've never seen anything remotely like this. And I am not shy when it comes to discussing issues around the use of epoxy. If it's possible to do something wrong with it, I have probably done most of them. But this is something weird like using urethane activator or something, or using contaminated reducer. I don't know.
 
My first thought was that you used something other than urethane reducer. Mineral spirits or enamel reducer would do what you were seeing.
 
Chris.
This has nothing to do with the activator; if the epoxy activator is bad, it will spray great and maybe lay down better than usual.
The epoxy activator is different from the clear and primers.
Here are a few things that can cause
Your issue.

1: Not stirring part A enough before activating.
2: internal strainer in gun or in a disposable cup.
3: Cold epoxy.

The disappearing, results from the above.
 
Hi guys (and Barry). Thanks for the replies. As always great support to be fond when using SPI products.

I hate to say this but I think this will remain a mystery.

From Barry's list:

1.- My project is a composite aircraft (epoxy glass). Mixing epoxy is so critical I have a timer on my bench to time the mixes (and tend to be anal with mix ratios). I mixed 75ml of primer in 3 minutes which is kind of overkill but that is what I have the timer set to. I also remix a few seconds before I pour in the gun because of settling. So I doubt it was poor mixing.
2.- I don't use an internal strainer per SPI recommendation. But I didn't strain this mix because of the small amount.
3.- Temperature was at least 70 inside the house (we are tropical beings so keep the house warm) where I store the paints. But who knows. I didn't measure the temperature of the primer. I have my doubts it was cold though (74 outside).

I used the epoxy activator, no doubt. Kind of hard to confuse. My epoxy activator is in a rectangular gallon can where the 2K is in a smaller quart (I think) cylindrical can. Colors (very noticeable) and smell very different. I am also trained to look for cloudiness in these chemicals and the activator was straw color but not cloudy.

Reducer is Medium Urethane. Clean. I did check the cans in my workbench after this happened so no doubts.

One thing I could accept doing wrong is maybe confusing the ratio when mixing (never happened to me but who knows). It's possible I misread the lines in the ratio column on the mixing cup and possibly added too much activator. But if this is like normal epoxy, more activator should not accelerate cure, you just end up with incorrect A-B mix and end up with a sticky mess that doesn't cure properly. Don't know if the primer acts like a regular epoxy.

My parts look good and not sticky (cured properly it seems) so I'll move forward. I will mix a little sample to see if it happens again. I do have two more small parts to paint so hoping the primer holds.

BTW, my airplane looks great on bare white epoxy primer. Get's lots of compliments and people asking what stuff did I used. In a years time I plan to top coat with SPI products!

I will post if I learn more.

Best Regards and Thanks,
Chris
 
My epoxy activator is in a rectangular gallon can where the 2K is in a smaller quart
NOPE:

Reducer is Medium Urethane.
What brand?
 
I can tell you from personal experience that straining the epoxy before it goes into your cup is a must. Thinking back I have had similar issues when rushing and not straining.
 
Need a tiny strainer for just 75ml :) but understand your point. But not clear how straining would have prevented the stuff from sticking to the cup walls. The hair ball maybe.
Chris
 
You must log in or register to reply here.
Back
Top