Sandblasting

btw thanks clubman for the in depth advice - i'm sure this will be of use to many folk

This is a big subject, just a few points for now.

1. Don't rely on shotblasters being gentle with your frame, or knowledgeable about the requirements of different types of tubing.

2. Masking. Best to mask anything fragile e.g. all threads, and the bottom of the steering tube where it joins the fork crown. Any wear at this point may cause the bottom ring of the headset to be a loose fit, which will cause juddering under braking.
   Chrome usually comes off only partially under blasting. The result is a mess - best to mask.
   Some blasters will pickle the work in a degreaser before blasting, ask about this, because it will remove your masking. Also, if any part of the frame is glued, as I seem to remember some Cannondale fork blades were, it should not go in the degreaser at all.
   Duct Tape is a good medium for masking, but it must be removed before painting because the adhesive melts in the oven.

3. Tubing. I'm some way out of date on this, but Renolds did not approve of shot blasting 753 tubing(bead blasting is ok), and I expect the same applies to 853 & 653. However 531 is ok, but remember you lose about half an ounce of material at each blasting. Cannondale recommended bead blasting, and I guess this would apply to any ali frame. Bead is lighter and finer than chilled iron shot, but much, much slower to use. Expect expense with this.

Personally, nowadays, I like the patina achieved just by wiping the frame with an oily rag.