Beadblasting 101

People wrongly think bead (as in plastic or glass beads) and sand blasting as an easy way to remove dirt.
It ain’t so: both of these are pretty expensive to buy and can be reused a number of times. Each has their application on vintage motorcycles.

Sand blasting
Insstead of using sand, it is likely your blaster is going to use Aluminium Oxyde (sometimes known as Coryndon), because it can be filtered and reused. It is designed to have multitudes of sharp edges, and usually in the 250 micron region. It is great for removing paint and rust and prepping panels etc for painting. Pressure at the blasting pistol can be up to 4 bar. Parts have to be clean or this will happen:

All this stuff will stay in the dirt and grease… not what you want! ot with a motor crankcase.

Bead Blasting
Is really meant as a surface treatment for alloys. The media has a ball-like appearance which make it bounce off the surface giving light polishing action.
It is also has less tendancy to stick to dirt leftover. Have a look at my cylinder head below and compare with the previous post.

Speak for itself.
Glass beads won’t change your surface appearance too much IF you use them as they’re meant to be ie, low pressure (I use 2 bars) and really clean parts.
They will remove corrosion as this flake off when hit by the balls. It’s always better to start with lower pressure and do two passes, instead of strting with higher pressure. It is a much more controllable process with low pressure. Also, if you use high pressure, the beads shatter when they hit the surface and then become abrasive as well as producing a fair amount of dust, neither of which is desirable.
A good example of how fine it can be: Some coin collectors use bead blasting to clean up some veryy corrded coins, but use 0-50my diameter beads and a pressure of 0.5 bars! Check these examples: A Swiss bead blasting company
The absolute best is beads used within a liquid environement, sometimes called Vacaperl or Aquajet. The same company proposes this ervice and have a look at their examples on motors.

Another way of using glass beads is as a prepolish treatment to ensure evenness. More about that later.