Help with Varnish

áI am having problems with my Epifanes varnish curing over my MAS epoxy. It has been 10 days but the varnish remains soft and easily damaged. The epoxy was well cured and properly mixed, non blushing and wiped clean before varnish application. Has anyone ever experienced this before? How should I move forward? I was excited to finish this cedar strip canoe but now I fear a lot more sanding is in my future!

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RE: Help with Varnish

Epifanes has several types of varnish....which one are you using?  was it one of their two parts?

is there something that makes you think it is the the underlying epoxy that is a problem?   have you tried the varnish on a clean piece of wood to see if it cures or dries on that material?

usually if there is a contaminant in the substrate (your epoxy) that is bad for the varnish, it will show as wrinkles or fisheyes ....not in a soft, easily damaged but otherwise visually good looking varnish.

my initial thoughts are temperature if its a single part and mix/ratio and or temperature if it is a two part may be the issue.  varnish, like paint definitely takes a number of days to reach full hardness.   low temps definitely elongate that but sounds like you have something else going on.

have you read epifanes tech sheet/advice for the material  for example, their one part varnish they say:

Common Problems:


 

The paint does not dry thoroughly:
The temperature is too cool for good flow, there is not enough air circulation, or too thick a layer has been applied. Applying too thick a coat may entrap solvents in the paint. Drying problems can also occur by applying a one-component product directly onto a "too fresh" epoxy or fiberglass coat. The required amount of time for thorough drying depends on the amount of solvents remaining in the original coat. In some cases thorough drying may not occur at all. These coats must be removed.

i would consider putting a call or e-mail into tech support at epifanes if you can't sort it out. 

 

RE: Help with Varnish

   Thanks for the response. Here is a little more information:

I am using the clear gloss 1 part varnish with the easy flow from the same company mixed 60/40.

varnish https://www.epifanes.com/page/clear-finishes

I applied the coat on a cool day that had a surprise rain storm, and from what I have read, humidity causes long cure times. I have been working on this project in a large 6 car garage with plenty of air flow, but no fans or heaters. It has been in the high 30's at night and 60's in the days for the most part.

I dont think there is anything wrong with the epoxy. It worked well the whole time I used it, and has cured for several weeks before attempting to varnish. I sanded lightly to give the varnish something to bite into. I did wipe the surface down with a damp cloth but no soap prior to varnish. After varnish application, all looked great until I came back the next day where I discovered several sags in the coat. Its almost like it had slipped off the surface of the epoxy...

I plan to call Epifanes on Monday but I am just blown away at how this isnt working how I had hoped. So much work has gone into this project and now a little more I am realizing. What does cured marine varnish feel like when properly cured? Is it going to be slightly tacky as some articles I have read suggest? It seems to me that the surface should not scuff or scrap off with minor pressure/contact with other surfaces correct?

RE: Help with Varnish

   I have used the same varnish several times with no issues. The 60-40 mix ratio seems a little off, typically the first coat is cut a maximum of 25%. With each successive coat you reduce the cut. In a perfect world [laboratory] the final coat goes on un-cut. You may have cut it too much, although I would expect it would have dried overly hard and brittle. Doubt it has anything to do with the epoxy. Good Luck!

RE: Help with Varnish

Mike,

Properly cured varnish should not be tacky or soft at all. It should be hard enough that it requires metal to scratch it, like a good coat of paint. From what you said about it sagging, it sounds to me that it went on way too thick. The outer layer cured somewhat, but there's still a semi-liquid inner layer that's causing the mobility. Those temperatures and humidity aren't helping, either.

Varnish is solids dissolved and suspended in a solvent. When you apply a coat, the solvent evaporates, leaving the solids in place. The smell is the solvent. There's also usually a reaction with the oxygen in air that causes some polymerization. That's what makes the skin on top of the varnish in an opened can.

When everything works well with a nice thin coat, the solvents let you paint on the solids, then evaporate and leave the solids exposed to air. The oxygen causes them to form a tough skin, which is your coat of varnish.

If the coat's too thick, not all the solvent can get out before the outer layer forms a skin. The skin blocks the interior solvent from leaving and the exterior oxygen from getting in, so you end up with a mobile liquid layer that allows the coat to sag and come off.

Solvent evaporation is obviously helped by higher temperatures. The air also has to "have room" for the solvent. If the air is already full of water (high humidity) , the solvent will stay in the varnish coat since it can't get into the air.

The oxygen reaction also proceeds faster at higher temperatures. If the temps are too low, it won't happen at all.

Products like easyflow exist to decrease viscosity by replacing lost solvent. If the reason that the varnish is too viscous is because of low temperature, rather than low solvent content, adding more solvent will just make the drying problem worse.

So my recommendation is that you do something about the temperatures, wait for low humidity and apply much thinner coats. Tthe brush should be almost dry.

Good luck,

Laszlo

 

   

RE: Help with Varnish

   Thanks, Laszlo. I just finished putting a second coat of varnish on my NE Dory, and the info you provided clears up a lot of questions I had about some problems I encountered. With your help, my third coat should be better. Jeff

RE: Help with Varnish

   Wow guys, this is amazing information. I appreciate all the help. Being my first time building a cedar strip canoe I expected issues but hadn't run into any until this point. I cannot thank you all enough for the advise. It sounds like I had a little too much varnish on the brush because I was almost flooding the surface like I did with epoxy. I will removed the coats I have on there now, and wait for some low humidity days to put much thinner coats back on. I will likely thin my first coat much less than before as well!

Thanks again

Mike

RE: Help with Varnish

   Epiifanes is my varnish of choice, for all my bright work, including my kayaks.  I am not familiar with their easy flow, I usually just thin using their thinner to get the right consistency and "feel".  I don't think I would try to remove what is there, I would try adding some heat somehow, and let the solvent "out gas".  Then do your sanding for both tooth and leveling.  Another thing you could try is using their wood finish that allows you to add coats without sanding between coats.  It goes on thinner, taking two or three coats to equal one of wood gloss, but that may help reduce runs and dry quicker considering the cool temps.   Epifanes does stay soft longer than some other varnishes, but, in my opinion, gives the richest finish. 

RE: Help with Varnish

   I've used the Epifanes WoodFinish and RapidCoat to good effect on the big boat.  I looked up the "Easy Flow" you mentioned, and that is basically adding extra oils to the mix.  I would possibly use a bit of thinner but not the easy flow. That's just adding a lot of extra oils to dry and cure in low temps, so no wonder it was slow to dry.  Since you are likely varnishing over epoxy like most of us here, I doubt you really need to thin it much at all.  Those instructions tend to be for bare wood, to get a seal and tie coat to the wood.  

I just started varnishing my spars for my Skerry today, in my MidAtlantic, unheated garage with just a small space heater and falling temps.  I applied a seal coat of epoxy before sanding for the varnish.  I'm using the Schooner varnish per CLC guidelines and it flowed on just fine straight from the can.  I did have to sight down along the spars to spot and correct some thick and thin areas as I went, but it is a bit thinner than the Epifanes or Schooner Gold that I'd used before, so it flowed well in the cool garage. I can manage to keep the garage at or above 50 degrees, so it should dry fairly well, though I'm not rushing anyway.

 

RE: Help with Varnish

 Laszlo,

If you had been the instructor 35 years ago, I think I could have actually enjoyed majoring in Chemistry.

Hooper 

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