Soda Blaster is a machine that fires Sodium Bicarbonate on to a hard surface, you will also need a dry air compressor (you can hire this).
It differs from pressure washers because it's low pressure and will only take off the soiling but unlike sand blasting is non abrasive so will not affect the surface beneath.
Where yachts are concerned it is used to remove, dirt,grease and barnacles from the hulls and all manner of other soiling.
Sodium Bicarbonate is not at all harmfull, in fact it is classed as food stuff, so it does not have to comply with COSHH regulations.
To find out more go to
www.branova.com where they supply and have all the info on Knightrum soda blasters.
Trevor