Why does my Epoxy come out all orange peely?

[kfz]

Well not all thew time, but for some reason I cant work out, about 50% of the epoxy unthickend as primer coating over bare wood, comes out orange peely and not smooth?

Ive been very carefull to makes sure the work and resin is at room temperture, I dont use any solvents or water to clear any dust, but still it does it.

Not mixing it right? The only factor that may well change.

I think its personally cos it doesnt like me, the feeling is mutual.


Kev

[davidh]

Kev,

how are you applying it? I use a roller and work it out well, I don't think it likes being applied to thickly? What epoxy are you using, 106 or 320?

I've found that you get much more even results by mixing less, working faster, then making another mix rather than trying to make one load for the whole job.

One final thought (if you're working in box 106 and 320) it is worth remembering that one has a mix ratio calculated by weight, the other by volume - and n'er the twain shall meet!

So - I'm think along the lines of thickness of application, speed of application and mix - in that order!

Dougal (apprentice to the epoxy king!)

[Ed]

Well....bringing this up could easily be right can of worms and people get all worked up about Epoxy...

So happy to give my thoughts for what they are worth, but I really don't claim to be an expert.

First, let me stick my colours straight up the mast on this.

In my very humble opinion, in the average amateur boat-builders workshop in the UK, Epoxy is a fantastic glue, the best thing to laminate with, makes great filler, but it is a lousy 'coating' for use as a varnish or paint.

Now, I know I will get knocked down by a million and one people who will tell us just how wonderful epoxy is as a coating....and how easy it is to use and to them - I say "Great, you are simply more talented, knowledgeable, richer, and have a warmer workshop than me". Now, I am not saying that I won't ever use Epoxy again to coat/paint with, I will and do so quite regularly, but I do so knowing that even though I have done it a fair bit, I will still have the occasional problem with it.

I also say to all those who claim how easy it is to use: "Then put down here on the Forum - exactly how you do it!" Because it sometimes seems like those who 'claim' to find it so good and so easy to coat with are also very secretive about exactly how they get reliable good results.....and that right annoys me.

Well first thing is that there are two problems that get called 'orange-peeling'. The first is when you get a flat surface with lots of little dimples, with , I think, the meniscus curving down to the substrate in a convex angle. This is true orange-peeling.

The other type is when you get large areas of coating that pull back to leave empty areas, with, I think, the meniscus curving down to the substrate in a concave angle. This also has a name, but I can't remember what it is at the moment. I am not totally sure about the 'convex' or 'concave' thing, it might well be my imagination, but that is how I imagine it, when I think about it.

OK...so having said that....what do you do about it.

Well.... I don't claim any of these ideas will work, but one may:

• Use a Coating Epoxy: Make sure you are using the right kind of epoxy - a good coating epoxy, not just a glue or basic laminating epoxy. SP320 rather than SP106 for instance

• Use a 'slow' 'very slow' or 'coating' hardener: Some Epoxies have a range of hardeners - so do make sure you are using the right one! It is much easier if you use the right kit!

• Apply it thin: Two thin coats are better than one thick one. To do this, you may need to either warm it or use a diluent.

• Keep it warm: Make sure you and the wood are really warm and dry. It is hard to get the correct conditions outside and/or the winter, if nothing else use a hotgun as you apply, or warm the epoxy first - at least bring it indoors first and keep it above a radiator for a bit. Try not to work on really humid days - this is worse than the cold!

• Use a diluent: I know - we are all told not to use a diluent with Epoxy - but this is mainly because it effects the structural strength of glues and laminates. I don't think it is so important with coatings, where you don't need that strength in the same way. There was once a BIG argument on this subject on rec.boatbuilding many years ago. Even the experts disagreed and I know we will here But in my experience adding a little diluent can make the guck flow and make the whole thing possible. If you use a diluent - you must use a proper epoxy diluent, not just any old thinners or acetone

• Abrade & Clean:Make sure the substrate is lightly abraded first - if it is epoxy, then sorry but you have to clean the surface with a good de-greaser. Some use Acetone, which I find ok, MKP may be better. Cellulose thinners can be suspect, but I do sometimes use - you can't use whitespirit/turps or anything oil-based. Then if possible just wash down with soapy water. Many epoxies give off an amine that leaves a coating on the top, which can be a right sod to coat over, it comes off easily with a little soapy water.

• Try a small area first: Always says it on the can.....but always good practice and keep a ton of rags to hand in case you want to pull it all off

• New Brush: Don't try and re-use brushes with epoxy. You can't afford to get the cleaner onto the epoxy. Also be careful as some brushes have some oil or something on them.

• Use a Peel-Ply:A bit wasteful this, I know, but it does save you from the work of sanding between layers. Just lie some peel-ply over what you are coating and then strip it off when cured. viola! perfect matt finish

You didn't mention whether this was a first coat or a subsequent coat, but I hope the advice will help anyway.

Or for that matter what the wood is - Some hardwoods are naturally very oily, which can be a problem.

I am sure there are other things you can try also and people will remind me of those.

But personally.....as I started off by saying. I just wouldn't bother. Use glue to stick the thing together and then use a proper coating system, like Blakes Woodseal (or even G4) to coat it.

Anyway, I know others will disagree....so let battle commence

cheers

eib

[Graham T]

It is also possible to get small bubbles forming and bursting to leave the surface dimpled if the epoxy gasses off whilst curing - thin coats in a reasonable curing temp helps with this but to be honest with me this sometimes happens and sometimes doesn't - I have not tracked down the cause but if I am using epoxy as a coating I always varnish or paint over so it gets rubbed down anyway.

[kfz]

Ed,
I competly agree with you. Plus the agrivation of turning a lovely pleasurable job of rubbing down a boom or rudder blade, wiping it down and giving it a coat of a lovely smelling varnish that takes 30 minutes every 2 years in favour of a complete nightmare of a weekend taken out of playing with horrid chemicals just isnt worth it. Maybe on a centrebaord case, but on something that fits in the car boot its just not worth it. I completely agree with you.

Plus I have learnt to never epoxy outdoors regardless of the weather, even in summer the temperature can drop enough to cause dew and cause it to go cloudy.

I will have to read your post again a few times, but I think my problem is in there somewhere.


David,

its SP Gurit SP106, general purpose with slow hardener. Bog basic stuff. And yes I may be mixing it badly, since you are correct in that its an altering factor.

Kev

[kfz]

Or for that matter what the wood is - Some hardwoods are naturally very oily, which can be a problem.

Ahh! Same conditions.

The centreboard, 7/8th marine ply, farily old, no problem = lovely finish

The centrebaord case. 1" of finest south american Mahgony, >50 years old and rubbed right back = a right mess.

I betcha if i put a second coat on it will go on fine now its sealed. Its does look like its reaction with the surface, At first I thought it was water (dont use thinners) but on no.2 I just wiped it with a cloth to clear the dust.

Kev

[jpa_wfsc]

Not enough styrene... which modifies the wetabillity of the epoxy.

[Ed]

@jpa_wfsc

please tell me more!

eib

[jpa_wfsc]

Just a thought - I was rushing last night too!

Gel coat = resin + Colourings and Fillers +styrene. The styrene is there to allow the gel to flow into the mould or, when brushed / sprayed on as a coating, to flow flat. Polyester gel cure is also inhibited by air - it is designed to set on the surface next to the mould, and remain softish inside - and the styrene at the gel - air interface allows the cure to take place. Varying the amount of styrene affects all these properties. Undercoats - no styrene, so the surface stays sticky and the next coat adherers well. Top coat more styrene to allow a good finish and surface cure.
http://chrischow.wordpress.com/2006/10 ... g-gelcoat/

Therefore surely adding styrene to epoxy when used as a coating should help, I thought. Then I remembered that epoxy is not polyester.... and Gel coat is polyester. Except when it is epoxy and I suppose behaves differently....

I am probably wrong then!

[Ed]

Well....I don't know, which was why I was asking.

But I have never heard of styrene being used in a normal epoxy....though it might be used in Epoxy Gel-coats.

I think I would be worried though about adding to a normal mix of guck.

eib

[davidh]

hate to say it but I don't think so....

D

[JimC]

Not enough styrene... which modifies the wetabillity of the epoxy.

That sounds like a remarkably terrible idea to me...

At best the styrene won't react with anything but will just hang about in the otherwise cured laminate as nasty smelly gunk slowly oozing its way out over time and providing some sort of permeability of the resin... At worst - it could mess up with the cure of the epoxy components, weken the mix dramatically, alter its properties and maybe stop it curing at all...

I'm no expert in this stuff, but I have worked in other branches of the chemical industry, albeit very many years ago.

[Ed]

@jimC Fair enough!

What are your experiences with 'orange peel'?

Do you have any thoughts on avoiding it. My guess is that you have used more epoxy than most on the list.

Of course, mainly to glue and laminate. Do you coat in epoxy much? Any thoughts or hints not yet mentioned?

eib

[JimC]

What are your experiences with 'orange peel'? Do you have any thoughts on avoiding it. My guess is that you have used more epoxy than most on the list.

Almost no experience with orange peel. I have run into it once that I've noticed on Queenie's side tanks. 90% of the time when I've use epoxy its on modern construction or on surfaces that I'm going to sand aggressively. I don't epoxy coat ply decks, I just use two pot varnish on new and one pot on decks whose history I'm uncertain of. If I use epoxy on wood it will probably be as an adhesive, or to support very tired ply, most probably with a thin layer of light glass which would probably prevent it happening by locking the epoxy in place. So you folks all know far more about the phenomenum than I do!

It seems unlikely to me that its what I'd regard as a wetting out phenomenum per se, the theories about oils in the wood, maybe other contamination seem to make sense to me, but its talking from ignorance. The other situation where you get something like that is hammer finish paint. If my memory serves me right that happens when the solvents in the paint evaporate out at different rates, and halfway through the paint drying some of the components in the paint are no longer soluble in the remaining solvent mix. I can't relate that to what I know about epoxy cure chemistry, but that isn't very much, so maybe...

[davidh]

Ed,

coating with epoxy:

Under the guidance of the Ian Ridge - who did all his composite contenders with epoxy coated decks, I did my strip planked contender last year. I have a full range of pictures, I've not posted them on here as the boat is far from cvrda legal - but for the purposes of this discussion, the information will probably be helpful.

As I said in my earlier posting, the big issues are:

Thickness of application
Speed of application
Control of the mix

and yes, I got orange peel when I got these wrong. But follow the rules and I found epoxy not difficult to use and that is from someone who doesn't count themself as skilled in this matter.

The rules seem quite simple.

Prepare everything in advance
Multiple small mixes are far better than fewer large mixes
Work fast using fast hardener. Make no more than can be applied in 20 mins
Each mix has all new consumables
Roll out the mix so that you're not trying to apply too thickly
Reapply just as the first layer passes the tacky stage

When coating the 16ft contender hull, I did 3 mixes per full coating. We used a 4" roller with top quality mohair roller heads, for each mix we used a new head and tray.

Depending if you are using 106 or 320 (320 is more expensive but has a UV inhibitor, essential if you are going to coat decks - if you are spraying a painted surface yuo can use 106 okay)

For mixing, get the marked up mixing beakers, use a fresh one for each mix and it has to be stressed, be as close to exact as you can be - the 320 in particular is quite sensitive to mix quality. Latex gloves to mix, fresh ones to apply - the two of us got through a full box of 100 in a day! As soon as somethings been used, it goes in the rubbish bag - don't be tempted to try and remix.

Work the roller out in the tray and apply, 45 degree strokes, but make sure you do not apply too thick, better to do a 3 fine coats than 2 thick ones. If you get delayed and the tray starts to cook, ditch and start again.

Funnily enough, the problem with using epoxy is not the coating, but the flattening off afterwards. Even with a pretty smooth finish, it still took more than a day of longboarding with 80 grit to get the surface ready for the first coats of varnish.

Probably the biggest issue is the cost. Even with trade prices, coating the Contender hull and new foredeck in epoxy set me back a small fortune, both in the epoxy and the consumables. But you do get a wonderful surface that will take sprayed 2 pot varnish and willlast so well.

If I was doing a smooth hulled boat (yes, if I could get my hands on a Fairey Gannet) then sans doubt it would be coated in 320 and sprayed.

Yes, you can have problems of which orange peel is jst one - but to me, it's worth the cost and effort. If it is of worth to the string I'll post some pics.

D