I was just sanding my hotcoat (RR epoxy) and noticed white specks all over the bottom of the board. I had been sanding in pretty bright sunlight and I think that things got too hot and I rubbed sanding dust into the epoxy. The epoxy was fully cured (over a week) but maybe the sunlight on the dark tint heated things up to the point that the epoxy was soft enough for the dust clumps to get rubbed into the surface. Is this what happened? It does not seem to sand out so I think that I may just have to live with it. Has anyone every had this problem or know if there is a remedy that does not involve sanding down to the cloth? The attached photos show what it looks like after block sanding it with 150grit.
So what kind of “tint” is that? What makes you think it isn’t in the tint?
It is a blue tint from FoamEZ… it has looked fine during lamination and previous sanding- here is a pic from before I started sanding.
Just looks like pin holes with dust in them to me.
Have you blown them out with compressed air?
What happens when you wipe water on them? Disappear and then come back?
It has been my experience that Spackled EPS will sometimes show lighter colored specks in the lam. It may be due to the difference in the way it takes the resin. It may be that once you are done with the spackled blank, screened and ready to be blown off. The air will blow little loose chunks of spackle leaving small holes that accept the resin differant. Creates a speckled affect. I have an EPS board in a shop that I noticed little rust colored specks in it only on the bottom. I spackled the Blank myself, but had it glassed by a good local glasser. My thinking is that there was something in the spackle. Mattwho’s thread on shaping EPS highlights some of the problems on the shaping/glassing side of EPS.
They (surprisingly to me) remain white when water is on the board…I even tried resin over one spot, but the specks remained white.
Yes, it is EPS and I do have some of the lighter colored specks, but this is totally white and did not show up until I sanded the hotcoat.
I saw that once on one cedar board I glassed, but not to that degree. I assumed it was tiny pinholes in the hotcoat into which sanding dust accumulated. It appeared in the 220 wetsanding stage. It would not come out even with compressed air, so I had assumed it was like a sanding dust paste forced into the holes. Later boards I did not wetsand until after the second ‘hotcoat’ and did not have the issue.
Can you feel any slight depressions with the tip of a needle where the specks are?
Looks like aired out lam to me. Your blue lamination is also aired out . You sanded opened up some of your airbubbles dust got under or in then you hot coated sealing dust in.
That makes good sense to me Scott.
If you think it’s stuff embedded from sanding, try a scraper. Just hold a razor blade perpendicular to the surface and scrape a small spot, if the area cleans up, you can look for something larger to make it easier and more uniform. I’ve used razor blades to scrape across the board for small things. I have a small piece of steel that I sometimes use for scraping off wax. It also works for scraping a lam. I have pieces of aluminum flat bar 1/8" thick x 1" wide and I use it to scrape across foam or lams.
It could be small holes filled with the dust from sanding. I’ve had that problem, but usually along the laps when I’ve sanded down to the glass. It’s hard to get it cleaned out, and if you add another layer of resin over that you will never get them out. You can try using a pin and compressed air and try to get each one cleaned out, but you have a lot of them. Maybe a tooth brush with denatured alcohol.
hey mate.
its most likely in your fillers coats.
One cause could be your frothing up the epoxy to much which can cause the white marks. Adding xylene and wax also contributes if you use to much in your mix.
Second thing that may be the cause is due to the long gel time micro particles in the air settle in the resin, and the dark colour highlights them.