Charles, he's right to a degree. you got to keep moving and i mean fast. cut the air pressure down will help, but you've gotto move the sand fast enough to propell it to clean. Don't try to clean it clean the first pass, it kind of like painting, remove a little at a time, like putting on a little paint then back track. You'll really be surprized at how quick it'al heat up. I not talking like, burn you heat. I surgguest you get some thing old like a hood to practice on, they're back about worpping because of the reenforcement in them.