Does anyone use walnut or simular media to clean old paint from a fiberglass hull? I need to remove some bottom paint.

Steven,

Blasting media is like sand paper, you have to have the right size and the right kind for the right job. Walnut shells tend to be large in size to be efgfective for thick paint and therefore you will need a 3/8" or larger nozzle that = 200 cfm @ 100 psi - Make sure you have enough air before getting started or it will be a long day. Walnut shells are middle of the road as far as being gentle, you will pop blisters and peck weak holes in the gel coat. Make sure you mask all surface that you do not want to blast - lastly remmber anitfoulant paints are not good to eat, wear an postive displacement air fed helmet during this process. Do a sample or have a sample done for you before moving forward.

I've used regular sandblasting before for that job but it really only prepares you for yet another paint job.
I've heard excellent reports about 'soda blasting' but have'nt yet found anyone out here that does it.
You should'nt have much trouble over there though.
I'd really like to hear from someone who can describe what it's like though .

This is on my Sea Ray Cruiser, I will be repainting with new antifoul. Thanks James.

Sorry guys no magic out there - Soda blasting is gentle and therfore does not do much work, slow work = big money. Blasting abrassive are many - Soda for instance has a low particle weight and if the energy ( 100 psi) is used then that particle does less work - same size particle made out of steel grit, then the energy in that particle gets more work done. There is no right or wrong media to use. If you have an experienced operator theny they will make the choice of material, size and pressure, just like picking sand paper. First deciding factor will be the brittleness and thickness of the existing coating, next factor will be the soundness of the surface under the coating, then cost and time. If you do not have experience to back you up,,,I would guess at using walnut shells # 12/20 or 8/12 (grit size) and 3/8"nozzle 200 cfm air source, 100 psi standoff distance of 18" might be a safe way to go. Other abrasives are availible but walnut shells are cheap and blow away easily -