Liquitex pinline. Epoxy not adhering

I wanted to post my experience using Basics Liquitex acrylic paint (purple) for a pinline on an epoxy board.  I assumed anything acrylic would work, but for whatever reason, I cannot get epoxy to stick to this paint.  Initially, I assumed it was because I didn’t sand the line before adding epoxy - I was afraid to mess it up.  When everything was dry, I went back and hit the pinlines with sandpaper – and really hitting it to the point where some of the paint was sanded off.  I cleaned off the board, wiped it down to remove any oil, mixed a little epoxy and tried a few spots again. 

Within minutes, the epoxy fell away from the pinline again. Things were going so well!  To date, everthing about this board was perfect.  I mean perfect - It has uneven tint, seven blisters, and bumpy rails. More sanding is in my future.

I don’t know the reason your Epoxy did not stick.  I can only speculate.  For one thing Purple as a color is always mostly pigment.  By that I mean than any latex acrylic paint that is purple has less binding agent, fewer resins, fewer solids.  The additives are removed to allow for maximum pigment to be added to whatever the by volume amount of material is.  Example;  A gallon of “Deep Base” paint is nowhere near a full gallon.  Usually a gallon of deep base has 3/4 to 2/3 of a gal of base(ie. resins, medium, binders etc).  Things like Arylic Resin, Solids, Fish oil, Cotton Seed oil.   The 1/3 space is there to accommodate all the extra pigment that will be added to make the Deep Base Color.  In you case purple.  Purple is one of the most transparent colors and requires mucho pigment per volume.  All resins have difficulty binding to pure pigment.  That is the only thing I can think of in your case.  I do have a fair amount of expertise in Acrylic Paints.  Epoxy not binding to almost pure pigment would be my guess.   A possible solution would be to seal the pin line with Acrylic Sealer using a small foam brush.  A good all-around sealer is the Behr Floor and Tile Sealer in Satin.  Clean up the pin line (or remove and redo).   Touch up.  With a worn out piece of 220 or 320, barely sand the 24 hour dry pin line.  Seal with Acrylic Sealer using a small foam brush.  Try it.  I tHink it will work.  Lowel

McDing, Yes! That has to be it and thank you for the workaround.  This was particularly frustrating situation and I appreciate the detailed reply.  I am sure this will help others.    

Mr Mc Ding , re , you have a lot of expertise with acrylic paint , so , a question , I just painted a blank using Montana gold and it did not look right after it dried so I need to paint it again using a lighter color , in your opinion will painting it again cause a problem when glassing , i am thinking it will be ok , you 2 cents please .

As long as the paint you use to repaint dries flat.  It may even be necessary to lightly sand the gold paint before you recoat with your new color.  Golds dry funny.  Very uneven usually.  I don’t think you have to prime the gold although some painters might insist that you do.  How well your final coat covers is key.  One could do it, but you might have to double coat to get it even.  You are mostly working against the porosity of the surface and how well it fills.  Should not affect the glass job at all.  A good even lamination should hold well.

Regarding the Liquitex/epoxy pinline problem… I’ve had some success (but haven’t tried purple) using heavily pigmented polyester sanding resin for the pinline.  Lightly sand once it goes off.  I usually give the pinline a wipe down with a lightly dampened acetone rag just to pick up any uncured residue.  Then go ahead and coat with epoxy.  It has worked for me when I was having issues with water based acrylic for pinlines.

I’ve also had mixed results with various other sorts of coloring processes… Posca pens for example seem OK with some colors. not OK with other colors.  Epoxy wasn’t happy when I tried a color panel using water based paint with some acrylic floor finish mixed in.  An epoxy clear coat did some crazy fisheye stuff with that one.

Testing small samples  is always the best policy.

Absolutely!  If you haven’t done it before or have any doubt;  Do a test first.  Better than sanding a pin line or a whole panel off.  If you can, stick with what is tried and true.  What others typically do.  Paint on a sanded hot coat of Poly is usually trouble free.  The same process with Epoxy is sometimes problematic.  The problems usually occur with the topcoat.  One also has to realize that laminated cloth releases from a painted surface easier than it does from raw or sealed foam.  So you want to be sure you have a very good watertight lamination.  Over the years I have seen two boards peel like a banana from the nose to the tail.  Both were full painted boards.  Both started due to a pin hole sized ding at the nose.  One was a pretty funny story, but no time for that now.  

Thank you Mc G

The common denominator among so many train wrecks boils down to one thing…EPOXY.  

Ah ! Epoxy problems… Not so much posts nowadays… May be guys have less problems with it… LOL. Or most guys that use it stop to try to use it like poly.

Because most “surfboard epoxy” don’t have solvant they can be a bit funky to use as top coat (pin holes, fish eyes, low self leveling, etc…) There are specific epoxy top coat on the market that do the job better than lam resin but not as effective as poly top coat.

So if you want to cover paint with epoxy top coat be prepared to post " why my epoxy gloss…"

Sand your board to 80 grit, 180 where you pin line, paint pin line, let dry then poly top coat. Buff it to deep shine if you want. It ll look like poly finish LOL. 

Hi Lemat; I had all bad experiences with that method. Epoxy over epoxy and Epoxy over Polyester after sanding; different grits; different ways to clean; different climates; different rooms; different weather; plenty of test; all gone bad.

All those epoxies were not surfboards epoxies by the way. Used in a gap of around 30 years so not the same types or qualities.

Yes that’s an “old” problem when all epoxies contain component that inhibit polyester cure so never stick and peel off.

Epoxy I use don’t have this component, like most 2:1 resin used nowadays, so after let it cure well and good prep  poly finish work well. For sure when dings, poly finish spider web even if lam under is still good because epoxy can stretch twice more than poly before break. More poly is thick and lam is thin more this is a problem. Because you bet on an mechanical grip you must sand throughly epoxy so need an epoxy sanding layer or a sanded " sacrificial" glass layer or use a peel ply on epoxy lam. Some poly, iso or acryl/poly, have a greater elongation to break. 

Final update.  I switched to light grey, but the epoxy didn’t like that color, either.  I didn’t have any sealer around, so I switched to grey latex paint, as an experiment. It appeared this worked on a small sample section, but naturally, after sanding/prepping the board, the same thing happened.  It’s a strange case because the epoxy simply avoids the paint entirely, like parting of the sea.  It’s like there is oil in the paint somehow.  To prep, I sand, clean, then wipe with denatured alcohol.  The epoxy is from NJ and is their marine grade, slow hardner type.  The epoxy is high quality, and has been very easy to work with.  Everything else is fine, but the pinline…the trick to cover up my other mistakes…is the mistake.  It’s getting sanded/polished and will hit the water shortly.  Nothing is perfect.  First board in the bag.   

I cheat.  I use automotive pinline tape under glass.   (Greg Loerh showed us that one).   Works every time.   

With that said, I normally go for the clean cutlap so that I don’t have to use a pinline.  

There’s enough guys who have perfected epoxy.  I’d listen to them.

Then there’s other guys who can’t.

Stick with it, and you’ll make a much better board.  There’s also epoxy pin lines too.