How long to wait before painting epoxy?

[SScoville]

I'm planning to put the last coat of epoxy on my boat in the a.m. I wanted to put primer on the next day. How can I determine when it's ready? If I can't push my finger nail into it, is that enough?

[Todd Bradshaw]

Probably not. If you want a decent looking surface you would most likely want to give it at least a few days to cure, followed by sanding it smooth. This will both generate a surface that will hold paint or primer properly and get the surface smooth enough to look good once you finally do paint it.

[JimD]

You should wait several days, wash thoroughly to remove any amine blush, sand smooth, paint. Many people forego primer altogether when painting epoxy.

[JimConlin]

Epoxy takes a while to finish curing. This process is aided by temperature. If you can find a way to get the boat or part warm for a while, it'll help. Even in a SC winter, covering it with black poly and putting it in the sun for an afternoon would be worth doing.

Some people have had adhesion problems with alkyd (oil) paints over young epoxy. I suspect that the epoxy primers like Interlux 404/414 or Awlgrip 545 would be a better bet.

[SScoville]

I amgoing to sand before painting. And I am going to use Systems Three Yacht Primer followed by their water-based LPU paint. I'll just have to be patient. I was going to hit it with a heat gun to speed things up, but I don't want to screw it up by painting too soon- "haste makes waste."

[SScoville]

Thanks for the help.

[Ray Frechette Jr]

I have heard of stipulations to allow epoxy to cure at least 5 days before painting, Others have stated 2 weeks.

As you can imagine lewaving a boat sitting in a working shop for even 5 days impinges on work flow.

Yes, epoxy curing is heat dependant.

I have been known to stoke up the coal stove with a charge of coal a couple of times to pop up the heat to the mid 80's.

I then use Systems 3 epoxy primer and then pop up again to allow that to cure, and then apint with systems 3 LPU.

[SScoville]

What can I do to test the epoxy to know it's cured?

[eastern270]

I am using system three epoxy on my boat. I keep my shop at about 60 degrees. I coated the floors with epoxy using medium hardener 2 nights ago and was able to sand it no problem about 2 hours ago. You will know if it's soon because it will feel like your trying to sand something rubbery. The epoxy will build up on the paper and pieces of grit may come off the disk like little tiny rubber balls. That's what I have experienced when sanding to soon. I hope this helps and my floors are getting 10 oz glass cloth starting at about 5am. Good luck.

[AstoriaDave]

What can I do to test the epoxy to know it's cured?A little test sanding will tell. Once or twice, when I was really impatient, I wet-sanded day-old S3 GP resin when it was still not fully cured. Works fine, but you have to expect to trash the ROS if you use it in the wet.

[RodB]

I think your asking for problems trying to paint so soon after epoxy work. Epoxy needs time enough to cure completely...so I don't think "sandability" is the mark of how cured the epoxy is... but just how long the epoxy has cured. Fresh/young epoxy still gives off free amines for quite a while...and they interfere with paint drying... by interfering with the dryers in paint... Even with an ammonia/water wash and sanding... so, if you are in a hurry use a good primer... like Parker Paint's # 1640 basecoat.... (the solvent is Xylol [xylene]) and this primer applies very easily and sands like a dream.. about $25/gallon. Interlux has a similar product and of course there are epoxy primers available too.

The primer adheres well to the sanded and clean epoxy and provides a barrier between the free amines and the paint. I can only speak for System III epoxy, of which I have used many gallons... 100 % of the time when I have tried to paint atop fairly fresh epoxy, no matter the surface treatment... the paint's drying is inhibited... the solution..

1) add cobalt dryer to the paint... a few drops per ounce (if you cannot or will not use a primer).
2) use a hot solvent primer that dries no problem on the fresh epoxy (just plain thinned paint will have the same drying problems as the paint).
3) Give the epoxy plenty of time to cure completely...and perform the proper surface treatment... wash followed by sanding...
ie... if you can wait until the epoxy is completely cured ( in my warm climate.. I like to wait a few days in 90+ degrees, the longer the better... 2-3 weeks would be great) , then clean and sand the surface.. you can usually avoid using a primer and the paint will dry fine.

RodB

[Wild Wassa]

When to paint?

This is a very good question. I often ask myself this question.

It is 107F here at the moment at 11.29 pm, so when to paint is a very good question for here in SE Oz. Wanting or finding a truley cool time to paint at the moment, is totally out of the question.

I put 4 epoxy coats on a boat today and sanded between each coat ... but when to paint is always an issue, that I rarely get a say about.

Whether the paint lasts for longer that only one race does not matter to the majority of owners of racing boats.

When to paint is always an issue with me. I'm a professional boat painter, the guys that pay the bills determine the waiting time for epoxy to set, dry, harden, start to cure but not ever to polymerize sadly, before I'm expected to paint ... and it is always only measured in minutes on racing boats.

So I waited for half an hour today after the last epoxy coat was applied before I started sanding then painting today's job ... but on my boats, I'd wait at least 28 days with an average day temp above 20C, before painting.

The boat I worked on today, will race tomorrow ... and today's paint job was also cut and polished before sunset. I'm a 2 pack (ab)user.

What is your ambient temperature again? ... mine was 112.7F at 3.00pm today with a relative humidity of about 12% ... half an hour of waiting for the epoxy to set, worked for me today, before I started painting.

Warren.

PS, or stick your thumb nail hard into the epoxy and if the epoxy is so hard that it doesn't give much ... that's my best answer.

[Wild Wassa]

Duplicate post.

[RodB]

When to paint is always an issue with me. I'm a professional boat painter, the guys that pay the bills determine the waiting time for epoxy to set, dry, harden, start to cure but not ever to polymerize sadly, before I'm expected to paint ... and it is always only measured in minutes on racing boats.

So I waited for half an hour today after the last epoxy coat was applied before I started sanding then painting today's job ... but on my boats, I'd wait at least 28 days with an average day temp above 20C, before painting.

The boat I worked on today, will race tomorrow ... and today's paint job was also cut and polished before sunset. I'm a 2 pack (ab)user.

What is your ambient temperature again? ... mine was 112.7F at 3.00pm today with a relative humidity of about 12% ... half an hour of waiting for the epoxy to set, worked for me today, before I started painting.

Warren.

Warren, thats very interesting... please digress... How often are the bottoms of these racing boats resurfaced.... describe the procedure and explain why... if you don't mind..

RodB

[Wild Wassa]

Rod, you have just asked me to write a treatise.

OK then, you old tempter you.

Sit down Mate, light up your pipe, take off your shoes, ask your good lady to rub your shoulders to phase out the stress, chill out ... and here goes.

What was the question again?

Warren.

PS, How does one write about a totally zen exprience?

PPS, I'll be back soon young Grasshopper.

[Wild Wassa]

Rod, are you watching the current Pacific Louis Vuiton series from Nu Zild?

Did you watch the last Louis Vuiton series from Nu Zild?

... and did you watch the last America's Cup series, where the silver fern on Team Emirates Nu Zild was erased from the boat during the series? Almost totally removed.

I watched how the silver fern was slowly polished off Emirates Team Nu Zild. 11 races in total, that was it, before the silver fern couldn't be seen.

Hull paint on a racing boat is the boat's most expendable resource ... 12 races only, I tell the owners that a paint job is worth, if the hull is cut and polished properly, race after race... or several year's longevity if they don't touch the surface, I'll guarantee my hull paint jobs for.

A racing hull is a working surface with a short/finite life expectency ... that is it in a nutshell Rod.

Most boats that I prepare the hulls of for racing, I refinish from 4-6 times in a 12 month period. For the more serious owners, I prepare their boats before each regatta.

I have clients who's boats I refinish fortnightly. To them, their results make my fees most affordable.

I work in a results driven industry ... where the expense doesn't seem to matter. Where it is only the slippery results that matter.

Rod, would you spend 4 days at a time, regularly cutting and polishing your boat's hull. I spend 6 1/2 days a week with my arms above my head. Refinishing hulls isn't a job for weenies.

Warren.

[Lew Barrett]

Hey Warren, nice to see you on the these pages again!

[RodB]

Warren,

Thanks for the comments.. I'm just wondering what the basic procedure is (rudimentary brief description as to what is done and why...) to achieve these fast surfaces... what materials are used and how they are finished and why??? No long dissertation, just a basic description of the process if you don't mind...

I realize that these are not wooden hulls, but I wonder what, if anything... you take from your work and apply it to finishing a modern epoxy composite wood hull (strip/cold molded, sheathed with xynole or fiberglass).

RodB

[Wild Wassa]

Lew, Cheers Mate.

Rod, as you have gathered, I'd prefer not to deal with what is under the surface of the paint. I'm about constructing a perfect topcoat, not just making another plod boat.

I view the surface of a hull only as surface grain, not as planking or timbers swelling ... but about making the working surface, measured in microns/disturbance free and as smooth as possible ... no drag.

What you question, is almost unanswerable. Making a working surfsce is not a formula.

When I do a hull, I do what is needed to make the working surface as perfect and as drag free as I can ... I do the prep and refinishing, square centremetre by square centremetre.

Warren.

[RodB]

:)

I understand...

R

[Wild Wassa]

Rod, Cheers Mate.

I remember when you were building your boat, I was fascinated by the stages that you posted.

Every image that you posted I've analysed and thought about how I'd do what you had just done.

I might not have commented often .. but I assure you Rod, I've learnt and enjoyed a great deal from your postings.

I can picture every image that you have posted about the build of your boat ... especially the stages of the painting of your boat. Test me of you think I'm being flippant.

Warren.

PS, I found your boat, more intersting than any other boat posted on the WBF ... that I say, most sincerely.

[pipefitter]

I too, found Rod's boat to be one of the most interesting builds here along with the reasoned and documented thought process concerning the design, build and it's purpose. A good show of bringing wood/composite into the 21st century.

[RodB]

Thanks guys, she was a fun build. I am always open to different methods to achieve a task... Warren, you should have made some comments if you had good suggestions.

I am thinking my next will be a Herreshoff 30 foot Alerion... "Pleasure"... Nats last personal boat.

http://i40.photobucket.com/albums/e239/Prestoboat/Misc%20boats%20etc/txflatsfloatbow.jpg

http://i40.photobucket.com/albums/e239/Prestoboat/Misc%20boats%20etc/txflatsbowon-72.jpg

RodB

[RodB]

Comments from Glen-L's epoxy info online...

Before doing any finish work or applying finishes, allow the last coat of epoxy to cure 5 to 7 days at 70oF, longer at colder temperatures. Wipe down the hull with a water/ammonia dampened rag or sponge. This will eliminate the greasy feeling amine blush to make final finish sanding easier and minimize clogging of the abrasive.