Epoxy, sorry one more question about craters

General Discussion
1

Hi,

New member here, so first and foremost thank you to everyone who has been sharing on this forum, it means a lot when you don’t have anyone else around who can teach you.

Now onto my question, I’ve been using epoxy since I started making my wooden surfboards, recentlty I switched to EPS + wood only on the deck, the boards are fine and they surf well, from mistake to mistake I’ve learned my own little tricks to make it all work, what resin to use (resin research working great for me), how to lap, hotcoat, sand, additive F, controlled room temp, no dust around. It all meant lot of sweat but progress has been steady, each issue solved, but one, craters.

Little holes that form at the hotcoat stage and can’t be sanded away or filled up.

I’ve read here that it might be caused by dust, but if that’s the case, dusting the lamination with rug and then compressor air doesn’t seem to be enough (I don’t rinse my lamination with anything, after sanding laps I just dust off), so I figured the pros must be doing something else, either to prevent or to post-fix this.

Please help or I’ll have to re-engineer my whole process and I guess switch to PU + poly and god only knows what would happen with wood bonding, weight, flex and what not.

I’d love to hear from people who use Epoxy in production or people that do this on a regular basis and know for a fact that they just can’t run into this issue.

Theese are the boards: 

https://www.facebook.com/settembresurf

Once more, thank you so much for sharing,

Andre

 

2

Craters are more than likely due to oils from hands.

For any dust or airborn particals that could get in the resin there are two tricks I use.  First trick is the lint roller.  It gets the dust off without getting it airborn.  Works great.  I use this with Poly too before gloss coats.

 

Second trick is just before getting started I use a plant misting spray bottle and hot water to spray a mist of water  in the air in the work space.  The mist attaches to any airborn dust and brings it crashing to the ground.  Do this before bringing the board in and putting it on the racks.

 

3

Thanks for the advices mako224, forgot to mention earlier that I wear glowes start to finish when handling the board, I guess that doesn’t prevent contamination 100%.

I can see myself going through those stages for my current backyard production, but I can’t see a real production scenario where people are tasked with rolling the boards or spraying the air prior to hotcoating, some of these boards are made in huge factories, there must be some other trick that is trivial yet bulletproof, no?

 

4

Yes, they have completely separate places to glass boards with controlled environments.  For those of us who shape glass and sand all in the same space we need to take extra steps.

5

I don’t do all in the same place, I have a glassing room with controlled temperature set between 25 and 30 degrees depending on how fast I need to go.

So, to recap:

  • Gloves to avoid human oil from start to finish during all stages involving resin, check

  • Separate room with controlled temperature, check

  • After sanding laps I wip the dust out with plain cotton and air compressor, check

  • Brand new brush on each pass, check

- Brush is first passed on some tape to make sure it won’t leave bristles, check

Current temporary solution:

While I lie down the hotcoat I scrub craters with my fingers if I see one during the first pass of strokes, that fixes the crater if I see one…but those I miss will be there, usually at least one or two escape my sight.

What am I missing?

6

Doesn’t sound like you are doing anything wrong or missing any steps. How many craters and how often do you get them? One or two is normal, and if/when I get them I do the finger rub trick and/or dab a bit of resin to fill the hole with the corner of my brush.

7

Hi Jamie,

I usually finger-rub about two or three when I spot them, then regularly one slips through and stays with the board. They are tiny at the end of the day, but I’m after commercial quality and this is really bugging me.

Filling, tried that, I squeegee some little resin in the craters before I get to gloss coat, but that usually forms a little bubble that eventually dries and leaves the hole pretty much there.

I wonder, are people in production rubbing all those craters out with their fingers? maybe I need better lighting to spot them all?

But does that mean it’s normal to maybe find one or two of these little thingies on an epoxy board you buy at the local shop? 

 

8

Post pictures

9

Sure, will do tomorrow as I get the sun light, but they are tiny and isolated spots so there won’t be all that much to see I guess.

10

do you spackle your boards?

Just asking, because i had the same problem on my last board.

The boards before have all been spackled, mainly because of problems with the hotwire or deep scratches.

The last one came out pretty fine , i just sanded it to 220. I have used the same eps in all boards( 30 kg/m^3)

The amount of craters in the hotcoat was terrible. I thought it could be air under the lam, cause the lamination was relatively dry although i used the same amount of epoxy as always. when hotcoating the epoxy gets warmer when it gels and the air starts to expand and create these craters.

Just my thoughts, would be happy for some input too,

regards

j

 

 

11

Perhaps the contamination is coming from the compressed air , auto painters have special filters in line to keep out contaminates that cause fisheyes in paint .

12

I am not a production guy. I’ve done about 50 glass jobs with Resin Research. I don’t “squeegee” resin in the craters. I use my saturated brush and dab a drop in the crater, so it fills it in, even leaving a little bump above the surface. If it craters again, then you definitely have surface contamination. Do the finger rub and re-fill until the problem goes away. In Greg Loehr’s epoxy 101 DVD he does the rub trick, so yes, I imagine it happens to everyone. Two or three should be found and fixed during the hot-coat stage. Yes, perhaps better lighting would help.

13

Contamination can be attributed to a variety of sources… hands (ruled out), air compressor (already mentioned), sandpaper treatment (stearated), but most likely - the wood itself. 

I’ve had fits with certain oily woods.  Even problems with non-oily woods that maybe had some oily sections.  Multiple coats later, with sanding between coats, I still had the problem.  I think the oils in the wood surfaced with each coat.  I finally just hit it with a final sanding and sprayed U-Pol as a finish.

It is sometimes effective to wipe down the wood with a clean acetone rag and ‘prime’ the wood with a coat or two of thinned epoxy.  Watch for fisheyes in the primer coats and continue sanding/repriming until they’ve been eliminated before adding your final top coats.

There may be some woods that are just too oily. 

14

If that’s the case, then they probably disappear with a poly gloss coat.  In a recent thread Mattwho asked how commercially made epoxy boards were finished, and to my surprise there were several replies indicating commercially glassed epoxy boards were finished with a poly gloss coat.  For the sanded finish they are using some kind of sealer like Behr IIRC.

I sometimes get tiny and isolated little pits in my epoxy finish, but I’m not making boards commercially, so I don’t fret over stuff like that - wax it up and go surf!

15

I am repeating what GL taught me:

  1. after the lam, and after cleaning up the edges, darts and tucks,  lightly sand with 120 grit over the whole surface, you are removing the potential blush and contaminants, don't sand hard or you will cut into the tops of the weave and cut the overlapping fibers and weaken the board.
  2. leave the sanding dust on and don't wipe with DNA and especially not with acetone.
  3. only handle the board with dust covered hands or with paper towels
  4. mix about 2 oz of resin and spread it with a sqeegee over the surface to be hot coated, keep it very very thin, just a very thin  film over the surface
  5. when it reaches a  fairly sticky consistancy, mix your full batch and hot coat normally.
  6. craters be gone.

I have never had fish eyes using this method.

16

well dog my cats that’s the first I ever heard that one, will have to try that on my next glass job!

17

it’s called a cheater coat.  I don’t know how you can ever repay me for that tip. (ha) but it works.

18

Damn. That’s a new one to me, also. Does it also help avoid burnthroughs during sanding?

19

You can do it with same batch of resin. Most of “pro” epoxy workers do it like this: make your sanded coat mix, spread some with squegge (or roller for big surface as boat building) then finish with brush. Do it on a taky lam or on a dry prep lam like describe GregTate (just scuffed).

20

I’ve seen successful sand/wipe preps using Xylene on a clean rag immediately before the fill coat is applied.  This was on EPS with fiberglass/epoxy with no fisheye issues anyway.  I can’t seem to find Xylene anymore in California.

If there are oily wood contaminants surfacing through the epoxy, it remains to be seen what will fix the fisheyes.