epoxy hot coat--thinniing

hello all,  i am brand new to this forumn and relatively new to the board building world–I am sure this topic is done to death but. . .

I am using entropy epoxy and am convimced that hot coating doesn not need to be as fickle as it seems it is. When i mean fickle i mean with respect to fish eyes.  I am obsessed with these things and trying to understand them.  If anyone has some rock solid advice on how to eliminate these buggeres from hot coats and gloss coats i am all ears?

I was wondering if anyone uses a thinning agent to see if a reduction in surface tention would help?  I think i have heard about this in polyester hot coats soewhere down the line?  And if thinning is a potential way to go,  would you use acetone or some sort of acid?

anyways, I interested in what you all have to say. . .

Epoxy is finicky in terms of contaminants.  Your surface needs to be sanitary and you need to work clean to keep dusts and oils from your hands off of these surfaces.   The temperatures in your glassing area need to be within a moderate range (can’t be too warm or too cold) and you don’t even want a breeze or a fan running.   Your mix ratio needs to be accurate and you need to mix it thoroughly and slowly so as to not add air bubbles.   Pour it out evenly, don’t just dump it all in one place and move it around.  

Basically, most of what you see the glassers do with polyester fill and hot coats - that’s what you don’t want to do with epoxy.  You can’t use a whisk to whip your resin, you can’t move it back and forth all over the board and ideally you don’t even want to be moving fast.  

There is a lot of old posts & threads in the archives, you can access with the search function.

I am strictly epoxy, Resin Research or Fiberglass Hawaii fast. My glassing room is not clean. Half the time I glass outside. 

I agree you can’t touch the board with bare hands before resin work, & the air has to be clean and warm.

I tend to go very thin on my successive coats after laminating. I laminate pretty dry, with a foam weenie roller, then roll another coat to fill it in immediately after the glass is down & wet out. You can’t go back and fix a dry lam later.

When that dries I sand & fill coat very thin. Then repeat until I can sand with a sanding block & hit everything evenly, no high or low spots. Sometimes takes a few fill coats. If I need to put a thicker hotcoat on for some reason I will apply a ridiculously thin coat, when that gets tacky I apply my thicker coat.

Last coat I roll on a very thin finish coat with wax.

At that point I can start with about 220 wet & go through the grits to about 1000, thats pretty much it. Sometimes polish after that.

I don’t tell anyone what to do or how to do it, just share what works for me. There are plenty of guys here who do nicer work with epoxy than me. MiWie, ResinHead, and UncleD come to mind, but there are plenty others. Lots of discussion in the archives.

Always some problems with epoxy finish coat on dry clean scuff prep epoxy. The lay epoxy thin and paint over when tacky gives best results but most of time i go with a poly finish coat. Epoxy hot coat on fresh tacky lam go most of time right, i start by spread epoxy with squegge thinnly everywhere then i use a brush over.

Thanks gang–so i am aware of all the prep and no oils from hands and contaminants. But i am always trying to get better at this so thnks. Lately ive just tried to crank the room as hot as i can and let the mixed epoxy sit as long as it can.  I do this because i notice that all the bad fish eyeing happens as the wet coat sits and waits–  I am curious about a couple things:

huck–you are using a roller to hotcoat?  do you get a lot of bubbles? and you seem to do a lot of thin layers before you start sanding.  I notice a big weight difference in my boards even if i add a thin gloss coat after sanding.  Do you notice the weigh add up after you are done with all the thin coating.  Also I am very curious about the hot coating while your lam layer is still tacky.  Is this a normal way to address fish eyeing?


lemot–I always thought that poly could not be laid over epoxy?  Do you do this regularly and have good results?  Is it because the underlying layer is still tacky?

Yes I use a foam weenie roller to lam, hotcoat, and finish coat. No, I never get any bubbles, why would I? I “seem to do a lot of thin layers before I start sanding” - don’t know where you’re getting that from, sorry, but I definitely didn’t say that. I use relatively thin coats, with sanding in between, and the weight is minimized. No the weight does not add up very fast or very much when working this way, and thats one of the reasons I do it. You add more weight with thicker coats. Also, “hot coating while your lam layer is still tacky”, again I did not say that. Although I think some people do this, I don’t. I said I lam dry, and then go back over it before it sets, because you can’t fix a dry lam later - dry spots / weave showing will always show under successive coats. I laminate pretty dry, but don’t leave it at that. Its just the way I work. If you lam with a foam weenie roller then it would probably make more sense.  But I don’t hotcoat over a tacky lam. I hotcoat, or fill coat, after I sand the lam.

BTW, if you are using Resin Research Kwik Kick or Fiberglass Hawaii Fast Hardener you would not let your resin sit, you would mix it and apply it.  A warm room temp is good when working with epoxy, but I would never mix my resin then let it sit in a warm room for any length of time before applying it.

Yes, you can apply a finish coat of poly gloss over epoxy. There can be plusses and minuses to doing this, and there are alternative ways to get that poly gloss with epoxy.  Its in the archives, covered in depth, have you searched/ read through the many threads on epoxy? As far as applying poly over a tacky layer of epoxy, I will let lemat answer, but I sure didn’t get that from his response.

Microwave of the Part A for a few seconds will thin enough to make the resin flow nicely.  A little Additive F helps with sanding.

On tacky lam i use only epoxy, that way i have no fish eyes but still some pinholes from particules because i work in same room i shape and sand and don’t clean it so much…

For poly finish you must let epoxy fully cure, sand prep it with a coarse grit 80 max. Do a thin coat, ISO poly is better, no problème of adhésion but can spider where board is dinged like with poly lam. Repair as usual. For ultimate durability not as good as epoxy but a easier way to finish. It’s a sanded gloss coat not a hot (filler) coat, for this i use epoxy, on tacky lam.

I was wondering if anyone uses a thinning agent to see if a reduction in surface tention would help? 

My understanding is that the lack of surface tension is what causes fisheyes. Additive F, which has parrafin in it, increases surface tension. My experience has been that no amount of careful handling reduces fisheyes as well as using Add F in my fill coats. Occasionally, I’ll still see some separation on the bottom fill coat, but a drop of resin off the brush takes care of that. Years back, Greg Loehr mentioned giving the area that’s separating a good wipe with a gloved finger, sort of smearing the resin into the weave with your fingertip, then brush that out. 

You can set your resin cup in a pan of warm water in lieu of a microwave

I learned epoxy by making custom fishing rods for million dollar sportfishing yachts so by the time I ever put epoxy on a surfboard I was already well aware of all of the pitfalls.  Its all about being methodical and keeping everything as clean and dust & oil free as possible.  Your bare skin never touches the board once the glassing process starts.  When it comes to finish coats clean air is a must.  Don’t do anything that will stir up dust.   A trick from the fishing rod business is to spray an ultra fine mist of water in your work space before working.  The mist will cling to airborn dust and it will sink like a stone.  After you lay down your finish coat walk away and don’t do anything nearby that could get dust of any kind airboarn.  Good luck.

Mako’s water trick works well.  Walking away from it and not creating dust is an absolute must.

Walking away from dust.