How to make my own epoxy primer?

[mydauphin]

1. Don't thin Epoxy
2. You can if for none structural usage and not underwater, use a mix of 50/50 epoxy with talc. I buy the colored stuff used for chalk lines. I also mix it with black and blue and make a brown for use in furniture. I can make it transparent or opaque. You have to play with amount and batch sizes, because you know know it wants to set quicker.
But never thin epoxy... Oh by the way there are some excellent water based epoxy primers that can be thinned with water. I used those to prime if I have to sand it down.

[PAR]

Well there you have it Angelgroove, interest is raised and a new thread would keep it fresh and in a direction of your choice, though I do think the majority of precautions prescribed are well and good for production work. The under a shade tree repair person needn't be as concerned, particularly in light of the performance attributes of some of the polyurethanes.

And welcome back Teakcell . . .

[boat fan]

Is the molecular bond and thinning of epoxy such an issue on furniture ?

Most furniture is not made with even water resistant materials these days.

If it is not boat furniture ,why worry about dilution / thinning of epoxy?

I understand the importance of not using thinners with epoxy on boats or aircraft etc , but furniture ?

What am I missing here ?

[PAR]

There's no reason to thin epoxy on anything. Thinning epoxy dramatically weakens it, making other adhesives more desirable, so why bother with thinned epoxy when easy to use PVA can be used instead. So, yes you can thin epoxy if you want to, but why bother. If it's an attempt to improve penetration, thinning is the wrong method for epoxy. In fact, testing has shown the amount of perpetration has little to do with water vapor penetration on a substrate, so if this is the reason, it's not of much value.

[oceansswk]

I understand Do not thin epoxy, You can put gel coat over polyester, but not over epoxy. Now comes my question, why can't you put gel coat over epoxy, and what prep is required if you wanted to put gel over epoxy?

[boat fan]

Originally Posted by PAR

There's no reason to thin epoxy on anything. Thinning epoxy dramatically weakens it, making other adhesives more desirable, so why bother with thinned epoxy when easy to use PVA can be used instead. So, yes you can thin epoxy if you want to, but why bother. If it's an attempt to improve penetration, thinning is the wrong method for epoxy. In fact, testing has shown the amount of perpetration has little to do with water vapor penetration on a substrate, so if this is the reason, it's not of much value.

Yes PAR........... I was going to suggest PVA........Is there an issue with the natural oils in teak that would make pva unsuitable ? If not , I can see why it would be better than diluted epoxy.Why bother to dilute epoxy ? No good reason I guess. You would not normally dilute other glues ,and I would never do it anyway , but I keep hearing that people do . .

I just don`t see the need for expensive epoxy on interior furniture at all. Polyurethane for hard wearing surfaces perhaps .....?

[mydauphin]

Wood glue is actually pretty strong. Reason for epoxy is that does not absorb water and is more permanent. If you need thinner epoxy, consider those that are made thinner on purpose. You can also thin epoxy by putting retarder and heating slightly. I let it sit in the sun a little before mixing.

[PAR]

Oceansswk, gel coat doesn't stick to epoxy very well. Now, you can improve the stick a bit with modifiers, but again why bother. Gel coat is very difficult to apply, color match and environmentally control during application and cure, for the backyard guy looking to make a repair. Yes, it can be done, but it's difficult for a pro to get go matches and results and much harder for a novice as you would expect.

If you have made repairs with epoxy, the logical choice is paint, which a novice, in less then ideal conditions can do a great job with. If the repairs areas are small (very), you may be able to use special primers (bond promoters) and flow some gel coat into the repair. Good luck with the color match. How big area your repaired areas Oceansswk?

I agree Boat Fan, unless the joint is small and could benefit from the strength of epoxy or other reason you might need it's physical properties, there are several glues that are effective on interior furniture.

[Landlubber]

Funny how this has gone on from the original ask of epoxy primers and my comment about thinning the epoxy primer.

The attachment below is interesting, it does of course recommend that the epoxy primer (Everdure) in this case be thinned by up to 20%...as I have done for decades...this product was originally made in NZ by Epiglass (later bought out by International Paints)....the reason for thinning was to establish better penetration of the bare wood....PAR has advised me that this is not a good thing to do, for many reasons and I have accepted his advice as being "correct" (he is obviously a very experienced boatbuilder/repairer and one that does his homework, not just parrots off comments from other sources)...the article is still worth reading for those that may not have much experience in such things.....

http://www.yachtpaint.com/New_Zealan...0_61_62_63.htm

[PAR]

It's a small world Lubber and everything comes back around eventually.

I use to thin epoxy too, but my own tests and those of several industry leaders suggested I might want to change my tactics. The test data is very clear, unlike a lot of testing, where you come away with a big question mark over the whole thing.

The one test, done by West I think, which I also duplicated (because I didn't believe the results at the time) was a 4x4 chunk of balsa, cut from a 36" long piece (9 where cut from it). Each was drilled in the center on one side with a 3/4" spade bit, 3/4" deep, checked for moisture content, then weighed carefully and placed in a zip lock bag. One was completely encapsulated with 3 coats of unthickened epoxy, another encapsulated in a common thinned version of epoxy, another my own "special" thinned version an untreated base line of course and a few other variations, just for laughs.

Each had the 3/4" hole filled with water, was weighed (again), then placed in a 75 degree climate controlled plexi glass box (a plexi box in one of the bed rooms). No light, low humidity for 30 days and pulled the samples. I still didn't believe the results, so I've done it again a few times.

You could see the thinned epoxy literally leach into the balsa, but after 30 days it weighed more, much more then the completely encapsulated regular epoxy block which only picked up a net gain of .007% (yep, less the 1%). Neither my own or the commercially available thinned epoxy could even come close to this. In fact, further tests concluded that regular 3 pound shellac was nearly as good at preventing moisture ingress and polyester resin was superior to the CPES types of thinned epoxy products on the market at preventing moisture into the block of balsa.

The conclusions once the blocks were cut and looked at with a glass, were simple and you've all heard me say it previously; "the amount of penetration is irrelevant, it's the quality of the coating, that determines waterproofness". In short, the coatings ability to resist water vapor ingress is the only thing that matters, not how deep it's soaked in. How deep it soaks in, just proves it can penetrate, that's all.

[Herman]

Why not ask Teakcell about the materials that are available in his area, and work from there?

If one wants to thin down epoxy, I have a reactive diluent available, which co-cures with the epoxy. (actually normal laminating epoxy already contains a lot of these types of diluent, whether mono or bifunctional, like hexanediol)
However, I am not in Birma...

[oceansswk]

Par,
I appreciate your answers to my questions. I was asking the gel coat question for information only. There are so many post were people are using epoxy for repairs that it made no sense to me that no one is using gel over epoxy. When I watch the fiberglass repairman mixing gel with vinyl ester , or spraying gel over vinyl ester I understand why besides cost.

[Herman]

For repairs, gelcoat can be applied over epoxy. (after thorough sanding). Beware however, and make tests. Not all epoxy accepts gelcoat over it, and it inhibits cure. In my line of product I have epoxy for which I am sure gelcoat will never harden over it, and I also have products where I am sure it is not a problem.
This is being done on a regular basis. It will not give you full optimum bonding strength, but usually enough for repair work.