John - I wonder about this. With any collision, there's necessarily thermal energy created when the kinetic energy of the ballistic particle impacts an object. This energy conversion will tend to melt the dry ice and warm the impacted surface, though I can imagine the normal blasting detritus ricocheting off the impacted surface and that some of the thermal energy would be absorbed by the dry ice, since heat transfers from a hotter body to a colder body.
It might also be possible that the relatively cool atmosphere around the impacted body, created by the melting dry ice, might allow quicker cooling of the impacted body. I have trouble understanding the thermodynamics of how there is a thermal shock on impact that does what you state below. Please explain. I'd also be concerned for anyone trying to do this in an enclosed environment, like a garage, even if the door is open. Oxygen displacement is a serious risk here and can lead to asphyxiation (dry ice is, afterall, frozen carbon dioxide). A dead-man switch on the blaster would be a must, but lots of ventilation of the work area would also be a minimum requirement or at least a wise precaution. I also wouldn't want any casual observers in the immediate area, but I *would* want an observer to keep an eye on me, if *I* were to do this. What do the dry ice blasting shops that do for safety precautions? Spud [EMAIL PROTECTED] On 21 Oct 2002 at 14:32, John Nasta wrote: > That's the nice thing about dry ice. It melts and leaves no residue. It also > uses thermal shock to cause dissimilar particles to contract at different > rates and therefore separate from each other. For that reason, it does zero > damage to the metal. The other blast media all use abrasion. > > John Nasta ----------------------------------------------------- To Unsubscribe please visit www.chevelles.net/list.html To start a new topic, send mail to: [EMAIL PROTECTED]
