Small marks in epoxy (bit like fisheyes)... possible causes?

[GolferGraeme]

Currently trying to get some epoxy on the underside of my car before the weather turns and I'm having issues (big update on the thread coming as soon as the paint is on).

Paint is Jotamastic 80 with summer hardener (10-30°C), part A stirred with drill attachment for about 10 mins, part B not stirred (didn't look like it needed it) then measured out using two separate syringes (which did create quite a few bubbles).

Metal was roughed up with 120 grit and wiped 3-4 times with panel wipe and blue paper roll until clean. Also tried wiping down with epoxy thinners, same issue.

Temps were around 10-12°C so near limit of hardener.

Any thoughts on what my issue could be? Temps too low? Bubbles in paint from faffing with syringes? Blue dye from blue paper?

 

[julianf]

Bubbles in paint from faffing with syringes?

Syringes?

I had epoxy contamination from disposable syringe lubrication.

Failing that, have you done anything like leave your setup aired up for too long, and the auto drains have not emptied the traps?

 

[GolferGraeme]

Yeah medical syringes so can't imagine there's any lube in there.

Not sure what auto drains are - I'm new to epoxy and bodywork repairs - but the pot was mixed up and used within 5-10 mins.

 

[AVI_8]

Silicone in the surface, possibly caused by not properly cleaning the surface prior to paint application

 

[GolferGraeme]

Silicone in the surface, possibly caused by not properly cleaning the surface prior to paint application

Surface was wire wheeled to death, then rubbed down, then wiped down lots with panel wipe and epoxy thinner. Agree it looks like some sort of contamination but not sure what more I can do? I do have some crowsfoot cloth, could try wiping down again with that.

 

[GolferGraeme]

Maybe silicone got in from the syringes? Stupid question, but how would you normally meter it out? Just pour into pots straight from the tin and use the ml marks to get ratios right?

 

[AVI_8]

Surface was wire wheeled to death, then rubbed down, then wiped down lots with panel wipe and epoxy thinner. Agree it looks like some sort of contamination but not sure what more I can do? I do have some crowsfoot cloth, could try wiping down again with that.

Well if you’ve done all that I don’t know, but it looks as though some sort of contaminate was there.

 

[AVI_8]

Maybe there was a lot of contaminate there and it needed several applications with new cloths each time?

 

[Brad93]

Use paint measuring cups with built in ratio lines

 

[GolferGraeme]

Maybe there was a lot of contaminate there and it needed several applications with new cloths each time?

Yeah could be. I'll ditch the syringes, wipe it all down again 2-3 times with crowsfoot and try again.

 

[Brad93]

Yeah could be. I'll ditch the syringes, wipe it all down again 2-3 times with crowsfoot and try again.

The problem with silicon is it's very tenacious

 

[GolferGraeme]

Use paint measuring cups with built in ratio lines

That's what I'm using, but I'm only mixing up around 150ml a time and wasn't sure how to accurately get it from the tins to the cup. I guess just pour it, wipe the lips down with some cloth.

 

[Mr Fixer]

I'm only mixing up around 150ml a time and wasn't sure how to accurately get it from the tins to the cup

You could buy some weighing scales. Paint manufacturers normally give mixing ratios by weight. I’ve used the little measuring spoons too, if you want really small amounts.

 

[tigdlo]

That's what I'm using, but I'm only mixing up around 150ml a time and wasn't sure how to accurately get it from the tins to the cup. I guess just pour it, wipe the lips down with some cloth.

I use cheap drug dealer scales off ebay for small quantities of Lechler epoxy, I mix as little as 10g of primer with 3g of hardener.

If the TDS doesn't give ratios for weight you can weigh a quantity of primer and hardener to work out weight ratios yourself.

 

[GolferGraeme]

You could buy some weighing scales. Paint manufacturers normally give mixing ratios by weight. I’ve used the little measuring spoons too, if you want really small amounts.

I'll raid the kitchen in the morning

 

[GolferGraeme]

I use cheap drug dealer scales off ebay for small quantities of Lechler epoxy, I mix as little as 10g of primer with 3g of hardener.

If the TDS doesn't give ratios for weight you can weigh a quantity of primer and hardener to work out weight ratios yourself.

I've got some kitchen scales that are ±1g or so and I have the weights/densities written down somewhere, cheers.

 

[GolferGraeme]

Just had a thought where the contamination might have come from... I was wearing engineers/gripper gloves whilst wiping down and the panel wipe and thinners definitely ate into them a bit. I'll get some of the thin nitrile ones tomorrow, try again. Idiot.

 

[julianf]

Yeah medical syringes so can't imagine there's any lube in there.

Not sure what auto drains are - I'm new to epoxy and bodywork repairs - but the pot was mixed up and used within 5-10 mins.

If you search with the correct terms you will find that I had exactly the same issue, a number of years ago, with sterile (well, out of date, but individually wrapped) medical syringes.

The plungers on them, which is hard to believe, but is true, can be lubricated by silicone.


Anyway, you don't have to believe me. All you have to do is weigh out the mix without using the syringes, and see what happens.

Again, I was in exactly the same position as you!

 

[Misterg]

SML give mixing ratio by weight. The information to try and calculate it is surprisingly elusive (The density of the main component seemingly varies with colour and Jotun don't give a definitive number. )

https://www.smlpaints.co.uk/data-sheets/uploads/files/library/files/2%20pack%20weights%200314.pdf

(The ratio is 3.5:1 by volume, and I've yet to see a mixing cup that lets me measure this.)

I *think* the TDS recommends wiping with a water based degreaser... Just checked - it's the application guide

"Inspect the surface for hydrocarbon and other contamination and if present, remove with an alkaline detergent.
Agitate the surface to activate the cleaner and before it dries, wash the treated area using fresh water.
Paint solvents (thinners) shall not be used for general degreasing or preparation of the surface for painting due
to the risk of spreading dissolved hydrocarbon contamination."

I'm not convinced that's your problem, though.

 

[julianf]

If you search with the correct terms you will find that I had exactly the same issue, a number of years ago, with sterile (well, out of date, but individually wrapped) medical syringes.

The plungers on them, which is hard to believe, but is true, can be lubricated by silicone.


Anyway, you don't have to believe me. All you have to do is weigh out the mix without using the syringes, and see what happens.

Again, I was in exactly the same position as you!

Thread 'How have I screwed up this primer?'

Jun 15, 2020

Epoxy primer -

You can see at the bottom left of the second photo that the coat is thin, but some areas were much thicker and suffered just the same.

I sanded the steel and sprayed down one part with thinner, but not the others. But all parts are the same with the error. I still suspect improper cleaning.

I sprayed an alloy part also. Same error. Maybe a little less so, but still there.

Lechler product, mixed as per sheet.

• julianf
• Replies: 51
• forum: Paint, Metal Coatings and Media Blasting