Graphite problem

[preacher]

All the boats I have built with graphite bottoms, so far, have given me a little problem. Every coat of graphite resin experienced micro bubbles. I tried rollers, bristle brushes, expensive nylon brushes, hair brushes and still, every coat had ga-zillions of tiny bubbles.

I also tried to use plastic squeegees but had trouble getting a smooth layer that way.

Is there a trick I'm missing? Is this normal?

This Cape Fear is special to me and I really want it to come out smooth and good looking.

[Oldsparkey]

Not knowing how you do it but this is the way I do mine and don't have a problem with it.

I use the two to one pumps for the epoxy......

I take a small container , add the epoxy to it ( two pumps) then three normal spoons of the graphite and mix it together. Then re stir it to make sure the graphite is mixed in. Sometimes it wants to clump so it is mixed again till it is all mixed in. If I think it is not mixed then it gets stirred again. My favorite item to do that with is a flat bladed screwdriver.
If the graphite is not thoroughly mixed into the epoxy and some of the dry powder is there , even a very small amount , you will have small bumps.

I want to make sure it is completely mixed into the epoxy before adding the hardener , this way the clock is not ticking on it setting up and I have all the time I need.

Then I add the hardener ( one pump ) and mix it again until everything is blended. The clock starts ticking when the hardener is added to the mix.

The mix is poured into a disposable paint tray and then picked up on a roller and applied to the boat. At times there are some bubbles and when the application is done I will lightly re roll the coating. There can be a few bubbles but they dissipate when left alone.

So far all the ones I have done come out with a nice shinny , slick black bottom.

Chuck.

[jem]

do the bubbles form after you've applied the mixture while it's still wet?

[craiggamesh]

I apply with a roller in the evening when its starting to cool. After rolling it on, I lightly drag a foam brush across the top to pop all the little bubbles. Then as it cools at night any bubbles that may be forming will shrink back since the cooler air is more dense. If you do it in the morning, as it warms, any little bubbles will expand becoming bigger as the day heats up.

This has worked well for me.

[hairymick]

I don't worry too much about the little bubbles.

I apply as Chuck does and after 3 coats, sand back with 240 grit. A nist smoooooooth dull grey every time

[Phishtech]

In my limited experience with epoxy, I've found that if I mix the resin and hardener too fast, like whipping it up to get it to mix quicker, you stir a Brazillian tiny air bubbles into it, and they won't come out. It'll even leave clear epoxy a grayish color if you get too many in there.

[Oldsparkey]

do the bubbles form after you've applied the mixture while it's still wet?

On mine the bubbles are from using the roller to fast the slower I go with it the less bubbles , which disappear as the epoxy sets up.

As craiggamesh said , a light ( no real downward pressure except for the weight of the brush) dry brushing with a foam brush does a good job if the bubbles stay there.

Stiring the mix , I take it slow and not like I'm trying to make an omelet. If there are a few bubbles in the mix , they vanish when I pour the mix out in the disposable paint tray. That also helps to give the mix a wider area so it does not set up as fast as in a confined container.

[preacher]

do the bubbles form after you've applied the mixture while it's still wet?

No, while I'm applying the coat. Actually, some of the bubbles go away while sitting to cure. I also drag my brush over the coat after applying and that results in fewer bubbles but still a lot left behind.

I'm wondering if the foam brush, after I apply a coat, might reduce the bubbles even more.

Also, I try to stir carefully to avoid the bubbles, but my problem seems to be when I apply the coat.

[makenmend]

with some 4" foam rollers I picked up from Harbour Freight(yellow) I had bubbles,left them to sit awhile then tipped off with brush, came out fine.useing 4" foam rollers from Home Depot(white) had fewer and smaller bubbles,again tipped off and no problems. More pressure/faster = more bubbles. low press/slow = less.

Good luck

MM