Air Bubbles!!!

[Doug Canada]

Just glassed the outside hull of my (Osprey) canoe yesterday.
Several hours into the process I noticed small pin-head sized air bubbles in various spots on the hull.
You can only see them within (about) 16" of the hull, but it is enough to piss me off!
I did not have them in my past two projects!

What causes them?
What can prevent them?

Thanks & All the best,
Doug

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[Ralphw]

I would say its the epoxy gasing out. usually occurs mostly on the first coat.
i guess just sand the bubbles smooth and apply second coat of epoxy.

please correct me if I'm wrong

[JimD]

Yup, just sand 'em out for your next coat. One thing that might help is to apply the epoxy to a warm 'pre-heated' boat.

[David Stimson]

to elaborate on Jim's comment - If you paint or fiberglass a hull when it is cool, and then the shop gets warmer, the air in the wood pores will expand as the hull heats up and you get....... bubbles. If you apply finishes or resins on bare wood that is in a cooling phase, the air in the pores will contract and actually pull some of the finish into the wood for better bonding and no air bubbles.

[Steve Lansdowne]

It also helps to lay on the epoxy at a time when the air temperature will be cooling off subsequently, thus in the evening or when your air conditioned shop is cooling off (Hah!). The epoxy will have hardened sufficiently by the time the air next heats up to avoid any trapped air from expanding and creating the bubbles.

[JimConlin]

Put another way, don't do first-coatings of epoxy when temperature is rising.

[Doug Canada]

It looks like the bubbles are at or below the glass.
(Cannot sand out)
I did my first coat between 9:30 - 11:00am, second coat between 1:00 - 2:00pm and my third coat between 3:00 - 4:00pm (took the day off from work). Wanted a chemical bond.
Shop temperature ranged around 22 degrees Celsius (72F).
Had a de-humidifire going prior and during the project.

Doug

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