epoxy varnish compatibility problem

[Larry C]

All epoxies have different cure times. Some are a week or less before applying an approved finish others are a month or more. There has always been controversy in the boat building community regarding which finish is compatible with a given brand of CURED epoxy. with all the recent changes in these coatings formulations to meet environmental requirements, no one really knows if the coating they want to use is truly compatible with the semi-cured epoxy they have used. Only pre-testing will supply this info. Even if it drys and everything seems good, you won't know for sure if it it will hold up over time till you subject it to the environment. It may just fall off , turn cloudy or hopefully it will be fine .

[Chuckles]

I wouldn't blame the varnish. You shouldn't have a problem over cured epoxy. I am wondering if you used a "blush free" type of epoxy. If you had blush on the surface that wasn't properly cleaned off, perhaps that could be the problem??

Should not be a problem with blushing. I sanded it then wiped it down with acetone before varnishing. I'm going to give it a few more days... still some tacky areas this evening (now more than 4 days and counting)

[Chuckles]

All epoxies have different cure times. Some are a week or less before applying an approved finish others are a month or more. There has always been controversy in the boat building community regarding which finish is compatible with a given brand of CURED epoxy. with all the recent changes in these coatings formulations to meet environmental requirements, no one really knows if the coating they want to use is truly compatible with the semi-cured epoxy they have used. Only pre-testing will supply this info. Even if it drys and everything seems good, you won't know for sure if it it will hold up over time till you subject it to the environment. It may just fall off , turn cloudy or hopefully it will be fine .

I actually still have to apply the finish coats of epoxy to the ends and roof and feather them into to sides. I'll wait a good long time before I even think of the varnish coats. I will definitely do some out of the way test areas first (think on the inside of the skirt under the trailer)!

I would just love to get the hatch out of the workshop I want to get going on the cabinets.

[DudKC]

Now I have a question...what should the epoxy finish should look like after you sand it down to apply the varnish? The manual I got with the West Systems epoxy just said to sand it to 80 grit. It didn't really say how to do that, so I bought some 80 grit sand paper for my random orbit sander. I started on the roof and it really took off the shine of the epoxy, almost so it looked like bare wood.

I stopped quickly and did some research, on this youtube video (http://youtu.be/rNLQRRDaitE), the guy sanded his with 220, but he did take the shine all the way off.

Just wondering how to move forward here, I do have some 220 sand paper for the sander so that isn't a problem, I'm more wondering about how much I'm supposed to sand it. I have 2 coats of epoxy so it should be thick enough to sand, just how much is the question.

Thanks

[Chuckles]

well its been 6 days and there is still sticky areas in the varnish. Probably just going to strip it then give it a good sanding, add a fresh cote of epoxy, then start over with the varnish after letting it cure for a long long time.

I talked to someone at RAKA and he said to wait 5 days before varnishing or longer if the epoxy is slow to cure??? Thinking back, when I put on the last cote of epoxy it was during a cold spell so I probably had partially cured epoxy. At this rate I might wait until next spring before varnishing... that should be long enough

DudKC:
I sanded to 80 grit with my RO sander between epoxy cotes when using the mechanical bond method. I put on a scratch cote then sanded, a second to apply the glass then sanded to feather the edges that overlapped, and two or three very thin coats to fill the weave of the glass and leave a smooth surface. The last few cotes were done using the chemical bond method. With the glass you have a pretty thick finish and it would be difficult to sand to the wood without trying. Hand sand any edges so you don't cut through.

I sanded to 180 grit prior to varnishing. Typically between varnish coats you only have to scuff sand with 220 grit paper. with each sanding you are left with a dull whitish surface that looks like hell. The next cote brightens it right up.

[Larry C]

Now I have a question...what should the epoxy finish should look like after you sand it down to apply the varnish? The manual I got with the West Systems epoxy just said to sand it to 80 grit. It didn't really say how to do that, so I bought some 80 grit sand paper for my random orbit sander. I started on the roof and it really took off the shine of the epoxy, almost so it looked like bare wood.

I stopped quickly and did some research, on this youtube video (http://youtu.be/rNLQRRDaitE), the guy sanded his with 220, but he did take the shine all the way off.

Just wondering how to move forward here, I do have some 220 sand paper for the sander so that isn't a problem, I'm more wondering about how much I'm supposed to sand it. I have 2 coats of epoxy so it should be thick enough to sand, just how much is the question.

Thanks

Dustin,
If your applying epoxy over wood (no glass) 2 coats is probably not enough to be able to sand smooth without cutting into the wood . Now that you have sanded, I would apply 2 more coats, and try sanding with 120. All shiny spots should turn dull including the small divots, and the orange peel should be all gone. I don't normally sand any finer than 120 grit on epoxy. If you want a truly smooth orange peel free surface, the epoxy coating must be smooth, and dull before applying varnish.
Also, Use the best quality ROS sand paper you can find, and stop frequently while sanding, and scrape the disc with a paint scraper to remove any epoxy that has stuck to the paper.

Larry C

[DudKC]

Dustin,
If your applying epoxy over wood (no glass) 2 coats is probably not enough to be able to sand smooth without cutting into the wood . Now that you have sanded, I would apply 2 more coats, and try sanding with 120. All shiny spots should turn dull including the small divots, and the orange peel should be all gone. I don't normally sand any finer than 120 grit on epoxy. If you want a truly smooth orange peel free surface, the epoxy coating must be smooth, and dull before applying varnish.
Also, Use the best quality ROS sand paper you can find, and stop frequently while sanding, and scrape the disc with a paint scraper to remove any epoxy that has stuck to the paper.

Larry C

This is very timely advice, Larry. This morning I sanded with the 220 on the ROS for about 10 minutes before going back to the 80 grit. This took me about 2 hours to get to this point. But I did consider doing more epoxy because I wasn't sure if 2 coats was enough.

1. Do you think you can tell by the picture if I need to do 2 more coats of epoxy? I would say it is smooth and dull for the most part, but there were low spots in the epoxy where it got into the grain and it is still shiny. I only got down to the wood in a couple tiny spots, for the most part what you see is dulled epoxy that could be ready to varnish, but I do want to do it right, so doing 2 more coats of epoxy today isn't the end of the world.

2. Can you explain the orange peel? I didn't really notice anything like that on this epoxy so maybe I missed it?

Thanks!

[Larry C]

Dustin,
If your applying epoxy over wood (no glass) 2 coats is probably not enough to be able to sand smooth without cutting into the wood . Now that you have sanded, I would apply 2 more coats, and try sanding with 120. All shiny spots should turn dull including the small divots, and the orange peel should be all gone. I don't normally sand any finer than 120 grit on epoxy. If you want a truly smooth orange peel free surface, the epoxy coating must be smooth, and dull before applying varnish.
Also, Use the best quality ROS sand paper you can find, and stop frequently while sanding, and scrape the disc with a paint scraper to remove any epoxy that has stuck to the paper.

Larry C

This is very timely advice, Larry. This morning I sanded with the 220 on the ROS for about 10 minutes before going back to the 80 grit. This took me about 2 hours to get to this point. But I did consider doing more epoxy because I wasn't sure if 2 coats was enough.

1. Do you think you can tell by the picture if I need to do 2 more coats of epoxy? I would say it is smooth and dull for the most part, but there were low spots in the epoxy where it got into the grain and it is still shiny. I only got down to the wood in a couple tiny spots, for the most part what you see is dulled epoxy that could be ready to varnish, but I do want to do it right, so doing 2 more coats of epoxy today isn't the end of the world.

2. Can you explain the orange peel? I didn't really notice anything like that on this epoxy so maybe I missed it?

Thanks!

Dustin,
I see exactly what you are dealing with. Regular plywood has a "rough"surface. You really need to fill this surface if you want a super smooth surfaced to finish with varnish. Think about a smooth surface like a cars hood. Is yours like that? It looks to me that yours has the highs sanded, with lows still shiny. This is the typical surface seen with epoxy on plywood.
If you really want a smooth surface, apply several more coats of epoxy until the surface is sanded truly smooth. No free lunch here!

IMO/ Finish work is EVERYTHING! All the time spent building can be wasted on a poor finish. Orange Peel is the rough surface ( the surface of an orange) left after using a roller for epoxy or other finishes. If it's not sanded smooth, it leaves the "Orange Peel Effect" That doesn't affect performance, but separates the pro from the amateur, and IMO it looks like CRAP!!

[Chuckles]

Well I got sick of waiting, grabbed a cloth soaked with paint thinner, and started scrubbing. I ended up scrubbing almost 75% of the varnish off... right down to the scuff sanded epoxy. I worry about using paint stripper on the epoxy so I think I'll try more thinner with a scotch-bright pad then give it a few days and sand off the remaining dried varnish.

After a fresh cote of epoxy and lots of dry time I'll start over with the varnish.

[doug hodder]

Sorry to hear of your issues. I use the West System epoxy. I apply it with a roller and tip it off, check the web sites for application....You can apply additional coats without sanding if you apply it prior to it completely curing. I typically let it completely cure, then scuff sand with like a 120 and apply another coat. On this type of finish, (bright), just how much time you put into the base coats will determine how the final finish will end up. It's time intensive to put on 6-8 coats, but that's how I do it. With sanding between coats, you will end up with a really nice flat smooth finish. Prior to the top coat, sand it with a 220. It gives it a tooth to bind the varnish/ paint or clear coat. It also gives it a nice depth to the finish on a clear one.

The real thing here is that too many people try to push it and do things too early, or cut the number of coats on the epoxy. The epoxy is what makes it nice and smooth fills the grain and levels it all...All the top coat does is protect what's under it. There is no quick way to do it...it takes a fair amount of time and patience.

Temperature and humidity and your recipe for epoxy are your keys to making it cure completely. It has to be completely cured prior to the top coat. If it doesn't sand all powdery when you sand and balls up on the sand paper...it ain't ready to be top coated. While I'm not a fan of varnish as it needs attention almost yearly if it sits outdoors, (others may disagree but that's the general feeling with a lot of the wooden boat community) a good "tooth" on the sanding will assist in the finish. Do it in a fine paper, as an 80 grit won't be hidden with the top coat.

While I don't do varnish...it's possible that you applied it a bit too thick. It can be thinned with denatured alcohol I believe. I typically spray my woodies with auto clear. You may or may not have the capabilities to do that. However, I'd think that multiple layers of thin varnish with a scuff would be a better option than a thicker coat. Subsequent layers of varnish will melt into the previous ones and allow it to build up slowly. Just my thoughts...others may vary. Doug

[DudKC]

Got up early and did 3 more coats of epoxy on the roof and most of the front of the camper before I ran out of the resin. This brings my total epoxy coats up to 5 after I finish the sides, hopefully that is enough to get a nice smooth finish.

If anyone reading this is considering going with West Systems, I don't recommend the 105/205 mixture. The 205 is the fast hardener, and it's too fast for a large job. I used 105/207 earlier in the build and it was much easier to work with. I got out to the garage before 5 am this morning so my pot life would hopefully be a little longer, which didn't really help. I could only use a paint tray liner for 2 uses, I had to hurry because the 2nd use would start to heat up and harden in the liner within about 5 or 6 minutes.

The 207 hardener is a lot more expensive though, which is why I went with the 205 I guess. The higher cost is probably worth it for the better hardener.

Prior to the top coat, sand it with a 220. It gives it a tooth to bind the varnish/ paint or clear coat. It also gives it a nice depth to the finish on a clear one.

The real thing here is that too many people try to push it and do things too early, or cut the number of coats on the epoxy. The epoxy is what makes it nice and smooth fills the grain and levels it all...All the top coat does is protect what's under it. There is no quick way to do it...it takes a fair amount of time and patience.

Temperature and humidity and your recipe for epoxy are your keys to making it cure completely. It has to be completely cured prior to the top coat. If it doesn't sand all powdery when you sand and balls up on the sand paper...it ain't ready to be top coated. While I'm not a fan of varnish as it needs attention almost yearly if it sits outdoors, (others may disagree but that's the general feeling with a lot of the wooden boat community) a good "tooth" on the sanding will assist in the finish. Do it in a fine paper, as an 80 grit won't be hidden with the top coat.

Referring the the quoted portion of Doug's post, I found that the 80 grit in my ROS was a lot easier to use than 220 on my cured epoxy, but will scuff marks show through the varnish if I only use 80 grit and call it good? I believe Larry said he doesn't use finer than 120 on epoxy, and Doug uses 220 before his top coat. I'm wondering if I should do both 80 then 220, or just scuff it up with the 220, or meet in the middle? hmmm...

[Larry C]

Referring the the quoted portion of Doug's post, I found that the 80 grit in my ROS was a lot easier to use than 220 on my cured epoxy, but will scuff marks show through the varnish if I only use 80 grit and call it good? I believe Larry said he doesn't use finer than 120 on epoxy, and Doug uses 220 before his top coat. I'm wondering if I should do both 80 then 220, or just scuff it up with the 220, or meet in the middle? hmmm...

How fine a paper one uses depends on several factors such as the epoxy brand used, and the final finish coat product. I don't use Wests epoxy anymore so I can't comment on how fine to sand it. Also, Doug is using Auto Clear coat which is water clear, and will show any imperfections. I have found that 120 paper on a good quality ROS run at the proper speed, I can go direct to a quality marine spar varnish which gives a slightly darkened amber color. However, I sometimes do sand finer than 120. As your using Wests epoxy, going through all grits (80,120,180) to 220 may be prudent. Are you sanding between epoxy coats?
BTW/ if your finishing "bright" you should be using Wests 207 hardener as 205/206 will harden with a yellowish tint. 207 is very clear.

[DudKC]

However, I sometimes do sand finer than 120. As your using Wests epoxy, going through all grits (80,120,180) to 220 may be prudent. Are you sanding between epoxy coats?
BTW/ if your finishing "bright" you should be using Wests 207 hardener as 205/206 will harden with a yellowish tint. 207 is very clear.

I am not sanding between coats, I'm using the chemical bond. And I wish I had more of the 207, but as it is, I have a whole unopened can of 205, and I'm about at my wits end with the money I've spent on the build so far, so 205 it is.

I am using the clear gloss, water based, Varathane spar varnish. It is clear, so do you think that will show imperfections? Maybe I will do the range after I get my epoxy coats built up.

[Larry C]

Well I got sick of waiting, grabbed a cloth soaked with paint thinner, and started scrubbing. I ended up scrubbing almost 75% of the varnish off... right down to the scuff sanded epoxy. I worry about using paint stripper on the epoxy so I think I'll try more thinner with a scotch-bright pad then give it a few days and sand off the remaining dried varnish.

After a fresh cote of epoxy and lots of dry time I'll start over with the varnish.

Chuckles,
I still suspect the varnish your using as being the problem.....
IMO/ epoxy does need protection from UV, but using consumer grade "spar urethane" varnish is not the way. For UV protection you want a true marine grade spar varnish. Costs more per quart, but less per year of service. The four tried and true varnishes that qualify are: Epifanes Gloss, Interlux Schooner, Pettit Captain's and Flagship. Consumer grade single-part urethane resin is more susceptible to damage from UV than the traditional resin's. The spar urethane adds the UV protective additives to get back to "acceptable", while the marine grade uses the additives to increase protection and extend longevity. You won't find the real marine finishes at ordinary paint stores. Here's a good source: http://www.jamestowndistributors.com/userportal/search_subCategory.do?categoryName=Varnish&category=36&refine=1&page=GRID

[doug hodder]

Referring the the quoted portion of Doug's post, I found that the 80 grit in my ROS was a lot easier to use than 220 on my cured epoxy, but will scuff marks show through the varnish if I only use 80 grit and call it good? I believe Larry said he doesn't use finer than 120 on epoxy, and Doug uses 220 before his top coat. I'm wondering if I should do both 80 then 220, or just scuff it up with the 220, or meet in the middle? hmmm...

If you tip off the resin when you apply it with a roller, you don't need to use the 80 grit as 220 is all it takes. Cut up an epoxy roller into pieces, clamp it in a spring clamp and back drag the epoxy. It takes all the orange peel out of it. Once cured, the 220 allows for a smooth additional coat. IMO an 80 grit scratch is a lot to cover up prior to a top coat, unless it's a high build primer. How good your final appearance ends up only depends on what you did under it.

I'd take my time and get it right as this is the biggest thing that is going to be noticed when you first walk up to your trailer, cut a corner here and hurry up may only leave you with a "wish I would have done" moment down the road. Doug