air bubbles and vac pressure

hi everyone ,happy christmas to all,

i have vacuum laminated 2 boards and each time i have had air bubbles in the cloth and resin, i tried vaccing a single skin on the flat with max vac and although it come out really smooth and light there was still an air issue within the cloth , i hand laminated the next board which came out fine so i have held off making any more until i could think about the air problem,

what i believe is happening is that i am effectivly giving the resin the bends!

there are small air pockets within the cloth that you could hardly see under hand lamination but once its in the vac bag,although we generate pressure from the outside we are lowering the pressure inside the bag which gives the tiny bubbles the chance to expand, the best analagy i could think of is blowing up a balloon under water and bringing it to the surface or when you catch fish from the depths and their swim bladders expand as they come up,

i think the opposite must be true if you could use an autoclave , a pressurised oven , if you take the oven part away you have a pressurised vessel so by raising the pressure above atmosferic you will be shrinking the bubbles in the laminate as the pressure rises,

i have/nt tried anything out yet but thought about making something small to fit in some fins and seeing what happens, is this the reason Burt uses an autoclave?,more doors to open?,what do you think ?pete

the bubbles need an escape hatch …also watch your resin brands …

west and sp go like bubble bath and will create a bubble at every point in the weave …



thanks Burt, do you think its just an epoxy brand issue ,when i pressed the single skin i had the cloth and resin under then the wood on top so any bubbles could rise and be drawn through the wood and the bubbles were more numerous than before , the bubbles must expand if the pressure drops and vice/verse,the perfect senario would be to laminate in a vacuum then raise the pressure to oblitarate any air , i think i will go back to hand lamination its only a surfboard after all, pete