Looking for advice on how to avoid & how to repair these little white pinholes that appeared after sanding my hot coat? Picture attached
It seems like they’re filled with fiberglass dust and we’re not there before sanding the hot coat.
Looks like pin air. Lamination to dry
Under your topic heading it states “topics: epoxy glassing sanding” on my computer so I am assuming this is epoxy resin.
The second coat of epoxy you are calling “hot coat” was sanded and now dust is actually in the weave that was not sufficiently filled with your second coat of resin.
This will easily blow out with compressed air from an air compressor and you can do a thicker final coat of resin to properly fill the weave and sand/polish to finish.
You may have seen the 50 threads on how compressed air is the cause of all crappy glass jobs because oil or other debris from the compressor gets on the board. Debris and oil traps mount on to compressors to prevent this. To not have a trap on your compressor is amature hour.
Some would not even bother blowing this resin dust off. On a small area throw some resin on it and see the resin dust become clear again. I blow them out because the resin dust can get very compact in deeper holes and not get totally clear again because resin is not reaching the compact dust and not dissolving.
Also I notice maybe a fin box opening on the bottom of the picture. You might want to consider pre-glassing installation of fin boxes, leash plugs and vents with a fiber glass patch on top before glassing board. You can do this with most fin systems but some are designed for such installation and is very easy to get good at.
Your board should turn out fine. Blow out dust, thick final coat taping off rails, sand carefully to finished board. As you do more boards you will realize how doing the first step as perfect as possible makes each following step that much easier. Also times like you are experiencing are great because you will never be stumped on how to correct a problem you cause or when fixing others mistakes.
If that board has a hot coat on it, you were too stingy with the resin. A hot coat is supposed to fill the weave in the lamination and result in a failry flat, smooth surface. Dust collecting in the weave means the hot coat wasn’t even close to thick enough. There should be no apparent weave after the hot coat is applied, and still none after sanding.
I would try to blow the dust out and do another hot coat correctly.
I think when one is using epoxy, and buying it themselves, one might be tempted to mix only enough to do the task, and one can come up short and try and stretch it out. With cheaper polyester resin one can mix up considerably more and let it wind up on the floor without as much concern.
It does look like your lamination was a bit dry in that area, and if not that then your fill coat missed some areas and sanding made them obvious by packing them with dust. Some of them would disappear with the application of more epoxy, some would not.
Sometimes a fine clean wire detail brush, brass or steel, can get the dust out, and a combination with compressed air. I use a leaf blower on these final stages as I do not have a filter set up on my compressor, and to see if it will go clear I use Denatured alcohol on a clean napkin. If it stays white and more fine wire brush has no effect, out comes the fine sewing needle.
When laminating and hot coating, as my ambient light source is not great, I have been using a strong headlamp on high(700 lumens), and even though I do not yet require reading glasses, for reading, I find the
lens magnification and the headlamp reveals that which would otherwise have gone unnoticed. I doubt your lack of a complete fill coat could have gone unnoticed if you had had better lighting.
For reference an old school style sealed beam car 55 watt headlamp fed 13.6v would produce about 1000 lumens, so 700 lumens mounted on the forehead aimed where one is always looking, is an almost obscene amount of light. My current headlamp is a O-light H2R (90$) and its turbo setting is 2300 lumens, but it gets so hot at this output it can only provide it for a minute and would be blindingly bright for laminating anyway.
I find using a squeegee to first very slowly spread the fill coat around, then use the chip brush rail to rail then lightly nose to tail with the headlamp, has yielded my personal best results, but I am no pro laminator by any means.
My worst results were always from trying to stretch out too little mixed epoxy being a frugal dumbass, and lack of proper lighting to see properly.
Yea we are building out some new areas in the shop and my lighting was weak. I’m using Epoxy 2:1 Thin Resin from US Composites with a gram or so of Additive F.
In the past I’ve always been able to blow the little white holes out with a compressor after some Denatured Alcohol or Acetone scrubbing, but not on this one. I’m almost certain it went skinny with the HC resin on that tail and didn’t notice it. Thanks everyone!
More resin spread evenly. If it’s dust and it won’t blow out; wet it with acetone or Styrene.