curing epoxy

[pipefitter]

Wonder if anyone might know about this. When epoxy coating wood,I noticed that if I broke the gloss on the epoxy by sanding it seems to completely cure better. My intentions were to let the epoxy cure for as long as possible before it got to the paint stage. I have had the hull sanded for over a year and has been in primer for over a month now.The console has been left in unsanded epoxy and was coated before the hull was.The other day I sanded the console and as soon as I sanded off the gloss I got a whif of that memorable epoxy smell,like I had just coated it a couple days ago. Is it safe to assume that sanded epoxy will cure much better throughout than unsanded? I dont get that smell when I resand any of the previously sanded. Would it be better to break the surface on epoxy even though it is going to be a long time before painting?Also,unsanded epoxy seems to be alot more water resistant than sanded.

[Bob Perkins]

Pipefitter,

If it has been a year - your epoxy has cured. Most epoxy is 100% cured in 7 days.

What you are probably sanding off is Amine blush. It is a waxy substance that rises to the top of the epoxy while it is curing. You can normally sand or remove it with a solvent.

The sanded vs. non-sanded epoxy is equally water resistant. However, neither are UV resistant.

So you need to paint or varnish to protect the epoxy.

Hope this helps,
Bob

[Wild Wassa]

When epoxy is hard cured it sounds different to well cured epoxy when being sanded, I notice.

I find with Boatcraft Pacific's epoxy it hasn't really cured until it stops shrinking. This often takes about 30 days, unless we have had a hot spell which speeds up the process slightly.

In colder weather, it doesn't actually hard cure (like rock hard) for months or until the first hot spell happens, or I heat the shed because I'm tired of waiting. I notice that this happens with Smith and Co's Fill-It as well. This difference between well cured and hard cured ... as in really hard.

Smith and Co's Fill-It is almost unsandable after 24hrs (sanding at 17hrs is best), but after a few months of curing, it sounds like I'm sanding metal.

Warren.

[ 07-17-2005, 05:38 PM: Message edited by: Wild Wassa ]

[RodB]

I have had system III sitting around for many months some unsanded and some sanded...I notice no difference, but I always try to do an ammonia/water wash before serious sanding thus eliminating just sanding/spreading/pushing around amine blush into the epoxy surface as you sand.

Also, if you are coating an area that will not see the light of day and will just be double or triple coated with epoxy, I think it makes sense to just leave it glossy and do not sand it at all if your not going to paint it.

RB

[ 07-15-2005, 06:27 PM: Message edited by: RodB ]

[pipefitter]

Amine blush...the suspected culprit of bad bonds between epoxy recoats and/or paint.This brings another question to mind without starting another thread. Ok,I read/reread about amine blush alot before buying epoxy. I was always sure to wash the surfaces most likely above and beyond anything I read. When I went to paint my boat the paint manufacturer slipped and told me to get a different primer for priming epoxy coated wood. Supposedly,the epoxy barrier coat was needed to prevent amine blush probs with the paint.They said the wrong primer would be ok if the surface was thoroughly sanded/cleaned.Now then,if amine blush is to be a problem,wont the 2 part epoxy barrier coat suffer the same probs? Is it also amine cured? I know the hull was sanded over multiple times with 180 grit on the long file,washed it 3x with amonia plus went over it with denatured alcohol soaked paper rags using generous amounts of fresh rags. I dont get what the difference would be between using well sanded epoxy build up as opposed to the epoxy primer.Isn't the epoxy coating kind of the same thing?

[RodB]

Just a guess, but I would imagine when formulating an epoxy primer for painting epoxy surfaces... the two main priorities would be the ability to adhere to cured epoxy surfaces plus forming a very good barrier and surface for paint to adhere to. I wouldn'think any type of "blush" would be allowed in such a product...just makes sense. Perhaps the technology of epoxy primers was the early rendition of "non-blush" epoxys...

There are some on this forum with plenty of knowledge about this subject.
RB

[ 07-15-2005, 10:20 PM: Message edited by: RodB ]

[pipefitter]

After I found that the primer I purchased wasn't the right kind over epoxy or that it could be if the surfaces were very clean,I wasn't going to take any chances. I started to sand it off but it wasn't coming off easy. This reminded me of an old autobody tip. If the primer isn't adhered,you cant sand it to a feather edge.I was able to sand it just fine and it has been on there a few weeks now with no lifting,blisters or discoloration.So it is staying. If I am going to have to sand it off,another coat of paint is going to come with it.I did use non blush slow epoxy.The primer is sanded so thin you can almost see thru it so if it was going to lift,now would be it's chance.

[RodB]

Some folks are applying straight alkyd enamel to clean, sanded epoxy without any primer and its drying fine...per Kirby's... as long as the epoxy is cured well and washed off and sanded.

I painted over some epoxy underneath the sheer decks and some of the area was primed, some not... the epoxy was only a few weeks old in curing in this case... I noticed the paint atop the epoxy without any primer was tacky even a few days after application...even in our heat. Most of the epoxy on my boat has been cured for many months and been in our heat for awhile...

Like you, I washed all with an ammonia/water spritz, and then wiped her down with a plain water rag...then sanded and in a few out of the way places, the Kirby's dried fine on surfaces treated thusly, no primer.

I pretty much applied a good primer over all...to offer more protection and longevity to my paint job and to just do it right...plus the high build primer offers such a nice easily sanded smooth finish to paint on.

RB

[ 07-16-2005, 12:04 AM: Message edited by: RodB ]

[Wild Wassa]

Epoxy on epoxy is an excellent primer, on an excellent primer. There is not a better primer going than a well keyed epoxy unless colour blocking is required, when the painter is applying transparent or semi transparent coats of paints. In this case a solid colour primer is advised.

Using a high build undercoat (or sandable undercoat) has only one problem that I see. That is although they are designed to go over a multitude of different materials to save time and to reduce fairing time, they are inherently brittle. A few that I've see in Oz, have all come and gone or been reformulated just recently. Some manufacturers have withdrawn them from sale because of bad feed back. Used on the panels of an automobile which are stabe, they are perfect. On wood, sandable primers are the weak link in painting and the first layer to fail.

When spraying, solid colour primers are advised, because the are real time savers and save the painter from using more paint than needed.

I only use epoxy as my primer. Whether I'm to use oil based paints, polies, varnish or poly/oil blend varnish.

Yesterday I was trying to get epoxy off an oil-based paint (a marine enamel) on a friend's fibreglass hull, that he hurriedly put straight over the paint to fix a problem at the end of the season before last season. This is not recomended at all but I wish someone had told this particular epoxy, that it wasn't meant to work. I eventually had to grind it off.

Nothing is perfect in the real epoxy world ... except well keyed epoxy as a primer for paint.

I use amin free epoxy.

Warren

[ 07-18-2005, 05:44 AM: Message edited by: Wild Wassa ]

[pipefitter]

Sofar,all the primer is sanded nearly transparent. I painted the console over just the clear epoxy/no primer with hatteras off white and it nearly covered in one coat. Block sanded that today with 320 and that surface seems to be a better primer than the primer/surfacer I used on the boat. For one,the one part poly clogs the sandpaper much less than the primer does. Sands easier too.The sanded one part poly paint reminds me of sealed primer used on an auto.

[RodB]

You would think that an epoxy glassed boat surface being well cured, and washed off well...and sanded would be a quite inert surface with just about any type of paint able to stick to it fine...key words being " well cured" and "clean". Maybe because of the complexities and variations of many factors this doesn't end up being the case in many instances.

The Primer I used was from Parker Paint Mfg Co... Tacome, WA...(by Great Northwest Paint) #1640 Overlay Interior/Exterior Alkyd Flat Primer finish. From what I have been advised because the solvent base is Xylene... and hotter than mineral spirits, or turps... and the nature of this high build primer...it just sticks damn good to the keyed epoxy and applying two coats is a snap. You can just slather it on with a brush and sand it within a few hours. Sanding is quite easy and it sands beautifully to a very smooth finish. Obviously, Alkyd paint adheres to it really well. From using it now for several parts of my project, I don't get the impression that it is "brittle" at all.

The cost of this primer was about $25/gal and I think it allows for a really easily obtainable smooth surface. I could have just applied Kirby's to the sanded hull and decks, but I much prefer the surface obtained with a sandable primer like this. What I have ended up with is a boat that has all exposed panels glassed then primed with a tough primer...and sanded smooth... and then painted with Alkyd enamel. Keeping her covered on a trailer, I expect to get many years service.

I guess one could apply CPES to the keyed epoxy surface as a primer/bonder and then paint... but the cost is about $140 for a two gallon kit and you don't get the advantages of the high build primer as far as sandability and smoothness.

BTW, this weekend I taped off and applied the non-skid sections (ground black walnut shells) to my decks...and then I taped off my water line on my boat and applied two layers of primer to the topsides. I then pulled the tape. The 4" wide black bottom "boot" that shows up (epoxy with graphite powder) really looks great. It looks like you just dipped the bottom of the hull in a vat of black paint. Photos to come.

RB

[ 07-18-2005, 08:29 PM: Message edited by: RodB ]

[pipefitter]

I had put enough coats of slow cure epoxy on the boat that when I sanded it with the long board there was no room left for primer.I was under the impression from the manufacturer that I needed this barrier for the paint to work. The primer was more unruly than the epoxy. But after looking at my console with one coat of off white over epoxy darkened meranti ply,it will only need one more coat.I could have just saved 40 hrs of sanding bypassing the primer stage.I had already sanded the hull enough.
Another way to look at it is if I had primed it with the color then wouldnt I indeed have a primer the same color as my topcoat? I mean being I have to sand between each coat of paint anyways?In autobody when we use a flat primer surfacer we used to use a sealer over it.Atleast I have a comparison of sorts between the console and the topsides of the hull to see how each method holds up.
Also RB,I am glad you are making good progress on your boat.If the weather holds up this weekend coming up i will be coloring the sides of my boat.

[ 07-19-2005, 01:37 AM: Message edited by: pipefitter ]

[RodB]

It sounds like leaving out the primer would have been the ticket. I would if there weren't gained advantages of using a highbuild sandable primer. Don't you just hate spending so much time on a project that could have been avoided?

Well I ran out of Kirby's and had to order another gallon... hope to finish painting next weekend. I hope to move the boat to the trailer this weekend. I plan to begin installing most hardware, steering, engine controls, outboard etc in the next two to three weeks. I still have to get a leaning post, poling platform, and a windshield grabrail fabricated in Houston, which means a 4 1/2 hour drive down there with the boat. This painting is just like all the other steps in boatbuilding. Once you start to get it down, you are just about done.

RB

[ 07-19-2005, 07:59 PM: Message edited by: RodB ]

[pipefitter]

Now there's where I have it made. I build those things at work. I have to change the front legs on my console because i used scrap and drops to build it with on comapany time so I rushed it just to figure out the height the console needed to be. Lean post is a single seater and is really to be a leaning seat with room for a cooler under it. I figure I can stand up otherwise. A portable livewell goes under the console and a seat folds down over that or up against the console when not in use.I am surprised that company wont ship those items to you. We used to ship whole T-Tops as far as Michigan. Also to Ranger out in Arkansas.Are you using anodized pipe or powder coated? Anodized is much better and it comes in black or polished or brushed. It comes in gold also but I can't imagine anyone using that.I remember feeling like I was done when the woodwork and epoxy coating was all done.The prep and paint was more work I am thinking. I hope to get on the water by fall anyways.

[RodB]

My leaning post and poling platform will be fabricated from 1 1/2" aluminum pipe...very nice welds...white roll and pleated padded seat on the lean post. The lean post will also have a back rest and a removable foot rest. The poling platform will be about 32 inches high, about 36" wide, have two steps, and also be welded aluminum pipe...you know, the shiny stuff like tops and towers are made from on offshore boats. The windshield grabrail will go over the windshield and offer a grab rail on either side of the console. This type of fabrication, if done properly, looks great, and if not, can look down right awful. I selected a small company that does real good work and gave me a package price. Welding aluminum seems to take some talent and experience, I picked a good company.

RB

[pipefitter]

Yeah,thats what we use.It's polished anodized sch 40 1½" pipe. The OD is actually 1-15/16ths by the tape measure. Good that you could find someone to do good work.It will look great on that boat.

[RodB]

Over the past few years I have checked out several of the top notch flats boats like Hewes, Maverick, Dolphin etc and tried to evaluate the features and degree of quality of their poling platforms and leaning posts, plus other hardware accessories...etc. I have pretty much examined every poling platform I have come across in recent years to get a fix on its optimal features, etc. I pretty much did the same thing for the entire package for a flats flyfishing skiff. It really helps to learn vicariously from others too and I did pick the brains of a couple of flyfishing guides that I know.

RB

[ 07-20-2005, 10:27 PM: Message edited by: RodB ]