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

[GolferGraeme]

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

That looks exactly like what I'm getting, seems like mystery solved! Will report back tomorrow, cheers fella

 

[GolferGraeme]

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.

Very useful sheet, thanks.

Also good to know NOT to use thinners! But looks like my issue was the syringes so will try again tomorrow with the panel wipe and see how it goes, maybe get some alkaline detergent if still no joy

 

[jo1010]

Also in cold temps like that it does help to warm the paint in buckets of hot water - or microwave ( not in the kitchen tho )

 

[Keith 66]

Re mixing ratios, Use a straight sided container, Not tapered as that affects the ratio. Mark a clean mixing stick with ratio of your choice 4:1, 3.5:1, 2:1 whatever, I usually mark with a knife cut You can use centimeters, fractions of inches even cubits.
Stand your stick in your container & fill to the first base line, top up with hardener to the top hardener line. Its more than accurate enough for any paint we will use. For small quantities i will dip a stirring stick in the paint & drip it into the container.

As for the bubbles, I have had this often using west epoxy on wood, usually when you apply the resin then switch the heat on or put the part in the sun, any air in the pores of the wood expands & outgasses through the resin, It can also happen with solvent entrapment & of course silicone. In my experience silicone fish eyes are often bigger.
Worst was some beautiful flame figured honduras mahogany that i made some seats out of for a boat, It had been planed down, sanded but when varnished poxy fish eyes! Arrrgh! multiple sand downs & recoats ensued. Wiping down with meths seemed to help.
The timber had been counter tops in a bank so had probably had pledge silicone polish sprayed on it.

 

[norsa]

Blue paper! You're undoing your panel wipe stage. The blue is generally recycled paper that is dyed blue to make it more attractive. The panel wipe can remove the dye and leave it on your substrate.
Nick

 

[mr haynes]

Use spoons for small amounts.
Steer clear of the siliconed syringes