I was watching a TV home remodeling show the other day, and they were using dry ice (frozen CO2) pellets with compressed air to remove mold from the rafters in the ceiling of the house.

The mold was removed quickly and all that remained was a light dusting of wood particles. The advantages touted were that there was no water infiltration because the Carbon Dioxide dissipates into the atmosphere as a gas without going through a liquid stage and no abrasive grit remains behind to get into bearings and other delicate areas.

I think I might try it for paint removal. Has anybody here used this method of abrading materials?

Here's some info:
http://www.coldjet.com/en/index.php

Jack

I have heard of it being used. I think the Juanita Terminal has used it to remove paint prior to prep and paint.

I had a chance to play with it several years ago... It has advantages, but won't do some things, and is expensive (both for the media and for the machine).

It is magical on crap on rubber... so great for gum on the floor of a modern transit car.

It is great when dealing with lead and other hazardous materials... you ice blast a beam covered in white lead paint, get a clean beam, and a bit of white lead dust to dispose of instead of a pile of lead contaminated sand.

It is softer than other blasting media. It won't do rust... It is slower than sand on paint. It is really good on greasy stuff.

I would consider it for air brake parts.

In concept it freezes the surface coating making it brittle, then removes it.

I can testify to the use of dry ice and working with Cold Jet. We actually used the dry ice process to deal with the smoke damage in the lounge of the Pacific View. After the process you could no longer smell any smoke or tell that there ever was a fire in the lounge.

As to exterior use we had mixed results. As for removing the newer Amtrak 3M decals it really does not work well and barely budges the paint undeneath. It is like the glue from the decal acts as a hardner. We tried several test patches on various spots on the car including cleaning up of one of the vestibule steps. It almost made the steps look new. We also used it on one truck to remove the brake dust build on the outside of the truck frame and equalizer. It removed the dust and left the paint.

So in the long run it does work with mixed results. However it is time consuming and can be costly. We actually hired Cold Jet to do the work. However it is my understanding that you now can lease or rent the equipment from Cold Jet. I will dig up the pics from when we tried the dry ice blasting and you can see for yourself. If you have any questions please feel free to contact me.

Christopher Edwards
Batavia & Ohio Railway Services, LLC.

We have just finished using dry ice blasting for the second time at the Monticello Railroad Museum. First project was the interior of a RPO, this year was the interior of a diner. Dry Ice blasting does good removing paint from stainless or aluminum, very little good when the material is steel unless it is galvanized. Don’t try it on wood that you care what the finish is, it tends to pit the wood rather badly.

We’re told there is a high pressure rig (225 PSI as apposed to 125 PSI) that stands a better chance for taking paint off of steel.

Here’s the outfit we rented the rig from –
http://www.continentalcarbonic.com/dryice/

Bruce Backus
Monticello Railway Museum

This process was used years ago on the 3751 when they cleaned up the boiler... heard it went fairly well. Any 3751 folks care to add in with more info???

The wood particles illustrate the problem with the idea of using "evaporating" media on delicates. The rust, dirt, chips of paint that you blasted "away" don't really go away - they go everywhere just like the media. Use CO2 instead of sand, and instead of your bearings being contaminated with sand, rust dirt and paint... it's just contaminated with rust, dirt and paint.

Pellitized dryice blasting was used during the restoration of the 3751. The tender exterior was dryice blast stripped of paint. The boiler exterior shell was derusted and most important the boiler interior was dryice blasted. On the boiler interior the dryice removed all the scale but not the important gamma magnetite coating. What was left was a dusting of scale on the floor. The dryice escaped into the atmosphere as C02. On the total job what is good is the dryice blasting media is beneficial, it does not remove what ever substrate you are working on, only the paint, rust, scale etc. The underlying wood, metal is left unharmed and without a tooth that is caused when using sand or other solid media. Also as I stated the C02 leaves and there is not piles of spent media in every crack and crevass of the equipment.

Generally if a locomotive or car is being blasted then the restoration effort is most likely serious. If this is the case then important moving parts are removed, taped and or covered. Sand when used as a blasting media has bounce, will accumulate and will find its way into everywhere it can. The particles removed by dryice tend to end up on the floor rather than fouling the machinery as solid blast media tends to do.

Thanks for all the quick replies and useful information. This is what this board is really about, the sharing of ideas and experiences.

I'm looking forward to using this method on my next restoration project.

Jack

We used dry ice blasting to clean 4-6-2 S.P. 2472's boiler inside and out. It won't take well-adhering rust off steel, but it's effective on failing paint such as "cooked-off" exterior boiler paint. The great advantage is that clean-up is easy and no abrasive grit remains behind to chew up bearings (exterior) and injector nozzles (interior), plus it won't attack the steel interior coating, as mentioned above. We rented the dry-ice-blaster unit and a high-pressure air compressor (>200psi). The dry-ice-blast websites warn that standard air compressors (100-125 psi typically) are adequate for grit blasting, but are much less effective for dry-ice blasting than 200+ psi compressors.

We also tried dry-ice-blast experimentally on S.P. 2979 heavyweight lounge car (built by Pullman in 1912 as S.P. 3231 baggage-club car, rebuilt 1940 by S.P. Sacramento Shops as a full lounge with air conditioning & Art Deco interior, and renumbered S.P. 2979), which had multiple layers of paint: two-tone-gray from the 1940 rebuild, thick layers of quasi-Pullman-green from it's days as a wine-tasting room, etc. The dry-ice-blast was effective at stripping off the thicker top layers of paint, but typically left the bottom layer(s). When the car was stripped completely last year, we opted to strip it with pneumatic needle scalers instead. It's slow but effective, and total disposal cost for the resulting drum of lead-paint chips was only $250. If we had sandblasted off the paint, disposal costs would have been >$10,000. (same charge per drum for 99% sand, 1% paint chips as 100% paint chips.) We'll use this technique again on steel cars, but next time we'll wear anti-vibration gloves.

- Doug Debs

Out of curiosity, that much CO2 in a confined space such as a boiler barrel, what sorts of precautions were taken to ensure proper ventilation and monitor the air to avoid lack of oxygen suffocation?

Adam

We dry-ice-blasted 2472's boiler interior when all the tubes & superheater flues had been removed, the steam dome and auxilliary dome hatches had been been removed, and the firepan had been removed. So there was lots of natural flow-through ventilation. Also we kept the shop doors wide open and may have used a fan as well.

- Doug Debs

Any data on cost relative to conventional sandblasting ?

DPK