Media Blasting (Shot / Glass)
I'd like advice please.
I want to media blast the last remnants of paint and underseal off my Maserati Mistral before it is re-sprayed. I have removed most of the 'original' paint and filler with paint stripper, but the corners and creases are too confined to remove everything easily.
Anyway my request is about media blasting in general. I haqve a 50litre compressor that can deliver 220 litres / minute and a blasting gun that requires 160-250 litres / minute. The compressor pressure drops quickly when blasting (down from 8 bar to about 5), so I realise I have too little capacity, but the glass media makes no difference to the paint. It buffs it, but does not remove it. It has no effect at all on the original underseal.
I want to know what to change.
Is it a greater capacity compressor (greater air volume)?
Should I use a different blasting gun?
Should I use an alternative blasting media?
YouTube and the web in general have lots of examples of how easy it is when everything is right, but I've found little advice to getting it right.
Alternatively, should the car go to a professional media stripper? I don't have towing facilities or trailer but am West Sussex based.
I have used both soda and metal bead for blasting to good effect. However, you do need to make sure that your compressor is up to the job, as you suggest. We have a 150 litre compressor in the workshop that produces 10bar pressure and is perfectly adequate, yet at home I run a smaller 100 litre compressor that produces 8bar. I have found that this reduction is capable of changing the effectiveness of the blast media quite considerably, so a 50 litre version would definitely have less impact.
If I were you, I would look at hiring a larger compressor for a day and see how it changes things. Someone like HSS is probably your best bet in the UK.
If you wanted to try out a different media, then someone like Millar Soda Blasting will be able to help you. Their website can be found at http://www.millarsodablasting.com/ and I know from experience that if you give them a call they will happily offer the benefit of their experience with regards your setup.
Please be very carefull if you go to a higher pressure to blast the balance of material off of your prized Maserati , very cool and glamorous cars BTW.
Blasting at higher pressure creates a LOT of heat>> it can warp youir panels and create craters in the area's you are concentrating on.
Be sure to hold the blast tip in an angle rather than straight at the panel, this greatly helps from creating problems.
Under coating>> a restorer's nitemare>> no product on the markets really seems to work well, have tried just about all.
Most end up using light heat and a good old hand scaper, been there and done that.
I might recommend using a high temp/high pressure steam cleaner, it is amazing of how much it will peel off.
The last car we restored, was loaded with it, finally broke down and had it dipped and electro coated in primer.
Cost us about $3500. here in the States.
Do so hope this helps you out?
I think that you need to think about a couple of key things before deciding on a course of action...
1. How delicate is the area to be blasted? If it's structural eg Chassis then generally it's tough and able to withstand a good blasting but as John said panels will warp with heat and that could be a costly thing to put right.
2. What paint proccess are you planning on using? Most Primers work best over Shot Blasted steel but this is more aggresive so it can be a bit of a catch 22 if your panels are delicate.
My advice would be to speak to a local blasting company, one that some of our customers have used in your area is http://www.blast-cleaning.co.uk/
Hope this helps and nice car
Every car owner should always try and fix a defect on their car before taking it to a mechanic, unless it's obvious right away that it's something pretty serious.