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Uh, oh..... fibers? You could have trapped solvents right down in those rascals. We can run into this with natural cane and rattan materials in our wood shops. If you used some type of degreaser there are probably some trace amounts trapped down in there. Might try a heat gun gently over everything before you shoot...
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some parts seems more affected then others even do the application was the same... so yes possibly related to the substrat...
its carbon parts which i previously clear coated but then re sanded them back due to imperfection and recleared... in order to reduce vapor in substrat here is the process i was following and still got all those pops:
1. cleaned parts with 99% alcool before sanding
2. sanding 400grit then 800 grit
3. dry wipped and blow off the dust with dry air and shop towel
4. clean again parts with 99% alcool
5. let dry parts 1h in forced air environment (65% humidity in the shop)
6. tack rag on part to rive dust amd then clear coat...
I usually see some boiling action in the clear in the 2 first minute and then it stops but start to see the solvent pop criter 20 min after (around 5 min after end of flash time)
to see all those solvent escaping in the first few minutes and also still having solvent escaping after flash so much it leads me to beleive there isor a chemical reaction releasing vapor or way to much solvent or vapor in clear or in substrat... ?
Questions were what clear system were you using and how old it was and how old activator was and was it a fast slow or mid temp activator but never mind I don't think any of that matters by that last pic.
That first pic in your last post doesn't show very much, I assume it was just the Panel sanded out and cleaned before clear its not up close and doesn't show any detail.
The Last Picture Yes I see some bubbles But I also see what appears to be fibers or maybe its just dust fibers when you zoom in on it.
It may be possible you are sanding through the actual Resin system used and your into the actual Substrate of the Carbon fiber which is Bad It doesn't take much to get into the fiber cloth when you dont have a lot of resin to work with but would require another coat of Resin b4 clear coating if you had or at least a sealer of some sort.
Do you know what Resin system was used for the Lay up?
Not all resin systems are the same and not all are compatible with each other NOR are they all compatible with all Automotive/Aerospace type Paint systems, Most are BUT not all. Some require a sealer be used before Top coating.
In the Aerospace industry we use a crap load of Carbon fiber and other materials in Composite world as its light weight strong and relatively easy to repair with the right training, we paint the stuff for a reason.
In your case your trying to display the material used unlike a a fiberglass lay up which uses a Gel coat for the primary surface in the mold which may be painted or tinted you have none of that with the resins used with Carbon fiber lay up when its layed up for displaying the material, So your Resin depth to fiber could literally be one or two thousandths of an inch which you may have already sanded away and are now sanding into the actual material again that's bad and not in a good way.
Just the opinion of an old grumpy Aircraft mechanic that is just full of ****.
Last edited by Doright on Fri Jul 01, 2022 2:06 pm, edited 3 times in total.
A&P Mechanic, FCC General radio Telephone Operator
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i get into model/ high power rocketry. some folks in HPR are using carbon fiber for body tubes, nose cones, and fins( theyre hitting some seriously fast speeds and high altitudes). ive read of issues not only when trying to just clearcoat the CF but also with bc/cc, ss, and the dreaded spray bombs. some folks not having any issues and other having wrinkling, lifting, fisheyes, etc.
they determined the cause of the problems was in the brands of resin used in the layups.