Thread: Removing epoxy bleed through

100 grit tends to take timber down pretty quick. I would tend to start with something finer to give myself enough time to make sure I am not going through.

I wasn't sure ... are you using veneer or the plywood? you mean bleeding right through the plywood to the outer surface.

I can't imagine epoxy coming through the plywood unless there was a physical crack - might be a problem with my imagination and you could be quite right.

It I can imagine it coming through a veneer - through some of the cracks and grain structure.

MIK

Originally Posted by Boatmik

100 grit tends to take timber down pretty quick. I would tend to start with something finer to give myself enough time to make sure I am not going through.

I wasn't sure ... are you using veneer or the plywood? you mean bleeding right through the plywood to the outer surface.

I can't imagine epoxy coming through the plywood unless there was a physical crack - might be a problem with my imagination and you could be quite right.

It I can imagine it coming through a veneer - through some of the cracks and grain structure.

MIK

Thanks for the reply MIK. I am using veneer. I have cut back to the amount of epoxy used which does cut back on bleed through though there is still a bit of epoxy getting pushed all the way through. I will try with 120 grit and see how that works out and advise on what speed I should get the sander at?

With the sandpaper you can use anything if you use it carefully. If you had 180 I would probably go that way. Around 100 is about as coarse as you want to go for wood if you want to do follow up gluing or coating. See Q&A Preparing a wooden surface for gluing - sand, plane - Michael Storer Boat Design MIK

Mik, he seems to have resin leaching through the veneers, which is fairly common with thin veneers, even moderately thick ones. I've gotten some bleed on 1/8" veneers before, though much more with 1/16" stock.

There's no way to prevent them, but removing them before the epoxy has fully cured is a lot easier then waiting for the stuff to turn to rock.

Use a scraper to get the bulk of it, after which use whatever grit you like, that will eat it up at a faster rate then the surrounding wood.

Another way of controlling the bleed trough would be to employ a piece of Mylar on the inside of the veneer stack, against the form. You'll still get random bleed through, but the Mylar will mash it flat and smooth it out, so that subsequent coats of epoxy will easily permit it to blend in. If you not using encapsulation techniques (epoxy just as a veneer glue) then the Mylar will uniformly spread out the bleed through which will make sanding easier.

This of course, assumes you're bending veneers around a mandrel.

Originally Posted by PAR

Mik, he seems to have resin leaching through the veneers, which is fairly common with thin veneers, even moderately thick ones. I've gotten some bleed on 1/8" veneers before, though much more with 1/16" stock.

There's no way to prevent them, but removing them before the epoxy has fully cured is a lot easier then waiting for the stuff to turn to rock.

Use a scraper to get the bulk of it, after which use whatever grit you like, that will eat it up at a faster rate then the surrounding wood.

Another way of controlling the bleed trough would be to employ a piece of Mylar on the inside of the veneer stack, against the form. You'll still get random bleed through, but the Mylar will mash it flat and smooth it out, so that subsequent coats of epoxy will easily permit it to blend in. If you not using encapsulation techniques (epoxy just as a veneer glue) then the Mylar will uniformly spread out the bleed through which will make sanding easier.

This of course, assumes you're bending veneers around a mandrel.

Your spot on with what I am talking about.
I form my shells in a female mold which has an internal madrell which applies even pressure while clamping. I cut back the amount of epoxy on the outer ply (most of my shells are 10ply thick, approx 6mm) and I had much better results, still a little bleed through I hit it with the sander earlier tonight with 120gritt and it cleaned up really well though the internal ply still had a fair bit of bleed through, some areas seem saturated. The next time round I will cut back epoxy on the inner ply also and hope it has a similar result to the outer ply. I have been using 0.6 traditional veneer, I haven't had any luck tracking down 1/16" stock, I wouldn't mind giving it a try. Could you suggest some suppliers of 1/16" veneer?


Thanks

Sorry Steve, but I'm in the colonies, so you're on your own for veneer suppliers.

I wouldn't reduce the amount of epoxy used in you bonding process. I'd be too afraid of "starving" the joint. I think a better method would be to thicken the epoxy a tad. I'll assume you are using a moderately heavy bodied epoxy, because all I know about Techniglue epoxy is it's a thixotropic pre mix. In fact, I'd recommend you use West System or BoatCoat so you have more control over viscosity and laminate strength. From what I've read, Techniglue is great for bonding in anchor shields for a concrete pad, but may not be best suited for your application. With West or BoatCote, you could tailor the adhesive to your needs.

I'd thicken it with silica and wood flour to a moderately heavy consistency, say about like ketchup or heavy cream. This will probably keep it from bleeding through as bad. If it still does, then mix it thicker so it's like peanut butter. Of course you should "wet out" the veneers first, but I would do this with a squeegee or putty knife and apply very thin coats of straight epoxy (unthickened). This too will keep bleed through to a minimum and you can control the amount you apply very precisely too.

The techniglue is a gel like consistancy. The bond and glue line with the techniglue is great it is just the bleed which is killing me at the moment. I contacted atl composites who manufacture techniglue and west here in Australia and their tech guy was recommending and standing by that techniglue was the epoxy for the job. I have some west still so I will give you suggestions a try. I don't have any of the silica filler at the moment though I have some of the microfibres, will this be adequate?

Thanks

Naturally, the Techniglue guy would recommend his product. I bet he doesn't even know what it really is (type of epoxy) or what reinforcement materials are used in it

Microfibers works very well, but you'll need a thixotropic agent such as silica to make the mixture the consistency you desire.

Good call. I will give the silica filler with the west epoxy a shot when I can get my hands on the right filler and see why results I get. Do you think the west micro fibre fillers can be used with the techniglue to help reduce the bleed?

Micro fibers will improve the bond and physical properties of the cured resin, but not knowing what is in Techniglue has me at a disadvantage.

G'day Steve
what, exactly, is the problem with bleed-through that you are trying to resolve?
Is it visual discolouration of the veneer?
Or that it sticks to your mould?
Other?
cheers
AJ

Originally Posted by b.o.a.t.

G'day Steve
what, exactly, is the problem with bleed-through that you are trying to resolve?
Is it visual discolouration of the veneer?
Or that it sticks to your mould?
Other?
cheers
AJ

Hi Aj,

I want to reduce the amount of bleed through by the time I have removed all the bleed through (with a sander) I have almost gone through the outer ply (or inner) of the shell. When I get minimal bleed it comes off no problems with the orbital sander though lately there has been a lot of bleed. I first thought It could be the change in weather and it becoming colder that the epoxy is taking longer to cure while in the molds to the epoxy is staying wet longer giving it time to soak all the way through the veneers. It could also be from the pressure being used. To ensure the veneers conform properly in the mold 55-65psi is used while clamping. I know it is alot of pressure to use with epoxy though I have not had any problems with starving the glue line or any delamination. Is it possible with the amount of pressure the epoxy is getting pushed through all the sheets of veneer

I have no issues with the shells sticking to the mold or the mandrell. So really what I am trying to work out is:

-How to reduce the amount of bleed. I do not expect to stop it completely, just minimise the amout.

-Best speeds and sand paper grits are best to use to remove the bleed with out taking much material of the inner and out plys of veneer? I have been using a low speed as the high speeds seem to be a little aggressive on the veneer.


Thanks

Using a thicker inner most (on the shell) veneers will solve the bleed issue. Post curing might also help, but epoxy tends to work through capillary action when under pressure. If you use a fast hardener and get it to kick off quickly once in the mold (add heat), you could prevent much of this. Personally, I'd be inclinded to use resorcinol, urea formaldehyde, plastic resin or even a PVA at the pressures you're using in this mold. The pressure may be just forcing "fiber saturation" from the epoxy.

On average, how long does it take to apply the epoxy to the laminates and get them all clamped down in the mold?

Originally Posted by PAR

Using a thicker inner most (on the shell) veneers will solve the bleed issue. Post curing might also help, but epoxy tends to work through capillary action when under pressure. If you use a fast hardener and get it to kick off quickly once in the mold (add heat), you could prevent much of this. Personally, I'd be inclinded to use resorcinol, urea formaldehyde, plastic resin or even a PVA at the pressures you're using in this mold. The pressure may be just forcing "fiber saturation" from the epoxy.

On average, how long does it take to apply the epoxy to the laminates and get them all clamped down in the mold?

In my original set up I used PVA though the open time was to short and it tends to make the veneer curl making it a pain in the ass to work with. I tried Urea Formaldahyde in my original set up which was with a system which did not put out half as much pressure, I wasn't a fan of the UF becasue of it's toxcitiy. Resorcinol is on the cards though I have read it has a relatively short working time. It usually takes approx 30-45min to apply glue, lay up veneer in mold and apply the pressure. I cleaned up a spotted gum shell this morning using 120g and 180g on a low speed. It came up alright. it could be a little better.

attached is a pic of the spotted gum shell i cleaned up this morning