Soda Blasting

[Sterob]

Gents,
Has anyone had any success with soda blasting with a home compressor?
I am trying to find a setup that yields the desired results on alloy motorcycle parts and am not having much luck.
I have seem pics of items blasted by commercial businesses and they are absolutely beautiful, they look like factory finishes.
I am using a new 12CFM compressor, the gun is a gravity feed type that is rated a 7 CFM and I am using the granulated Bicarb Soda that the big boys use.( $66/ 25 Kg bag!)
I have researched on the Net as much as I can but can only glean a small amount of info and then, nothing specific. It's almost as if the process is a National Secret.....lol.
The nozzle on my gun is 6 mm and I thought that a smaller tip would give me high a velocity, and therefore better results but when I tried a nozzle with a hole of 3 mm, it just blew back through the vent. Maybe I need to go a little larger to 4 or 5 mm?...I may try that tomorrow.
As far as I can tell, the only variables are : air pressure, granule size and nozzle size.
Anyway, can anyone tell me where I'm going wrong? :?

[Master Splinter]

I thought soda blasting was a wet process...?

[pipeclay]

from what ive read your cfm is ok,nozzle side around 2.4mm any bigger and the amount of lpm goes up greatly,should be able to get some type of result from as low as 30 psi.your main proble will be regulating your flow rate of soda,may have to play with venturi sizes ,psi,nozzle size good luck if it works.

[journeyman Mick]

I thought soda blasting was a wet process...?


Yeah, I've been blasted on whisky and soda, not exactly a dry process. :D

Mick

[C-47]

Sterob,
I'm somewhat in the same boat, trying to get a satin finish on machine dials but using fine glass media, which I'm told is 200/400 mesh size. Several things I have learned and from input from others, the nozzle size can't be reduced greatly without effecting performance of the venturi action (I think you have probably found that out). My hand-piece spout was originally 5.3mm ID and reducing that to around 4.2mm appears optimal at this stage. Delivery pressure has been reduced, while I started at 100 psi this is now down to around 70 (still experimenting though), compressor output is about 15CFM and no problems keeping up. The material I'm blasting is relatively soft and the results so far have been fairly good compared to what I was using before. Still a lot to learn though I feel.

[station-rat]

Glass beads are the go!
Station-rat

[Sterob]

I haven't tried reducing the pressure much yet, but I'm not sure that is heading in the right direction as soda works by splattering as it hits the job ( this is what does the cleaning) and my particles don't seem to be splattering at all now.
My nozzle dia is now 3mm, but now the gun does not work as it should, which make sense regarding the venturi, and going larger will not increase the velocity of the medium so it will splatter......looks like I'm cooked.....
I can adjust the media flow rate via a knob on the side of the gun.
The glass beads are alot higher on the 'hardness scale' and may be defeating the purpose, for me.
Maybe it just needs a ludicrous sized compressor like the professional cleaners use and it can't be done in the home workshop?

[specialist]

Don't know about soda blasting, but when sand blasting with the full size unit 250cfm compressor and pot, more product in not neccessarily better. maybe you need to reduce the amount of soda, while still maintaining the pressure? Works with sand:D

[C-47]

Sterob,
I think you can get down to a nozzle size below which the venturi becomes inefficient without a large increase in incoming pressure and even then I'm not sure the convergent / divergent ratio would be correct, too many moons ago since I studied that stuff. The gun I'm using at present is a Sampson (Ozzie made for a change) got it from Belmont Tools (usual disclaimers) and I think the venturi is 3mm ID. If you get up to Perth you are welcome to try it out with your media, my system it total loss, no cabinet at present.

[Sterob]

Sterob,
I think you can get down to a nozzle size below which the venturi becomes inefficient without a large increase in incoming pressure and even then I'm not sure the convergent / divergent ratio would be correct, too many moons ago since I studied that stuff. The gun I'm using at present is a Sampson (Ozzie made for a change) got it from Belmont Tools (usual disclaimers) and I think the venturi is 3mm ID. If you get up to Perth you are welcome to try it out with your media, my system it total loss, no cabinet at present.

Hmmm....sounds like I'm way out of my depth....lol
I may try increasing the nozzle dia in 1 mm steps and see what results I get. If I go too far I can just make another one on the lathe. I don't know what size my venturi is, I may have to pull the gun down and have a look. I got my gun off Ebay in the US but a mate found the same one in Perth somewhere.

[durwood]

Sterob,

Your info seems to be a bit off, can you clear up a few points.

Is the gravity feed gun made to sand blast? sand blasting guns are not usually gravity feed, gravity feed is not really suitable for products which will pack down when placed in a container. sand blasting guns draw the material up into the air stream to be blasted out of the nozzle.

Are you sure its rated at only 7 cfm? Thats tiny !! usually a gun using only that much capacity would be a small spray gun spraying thin paint not much better than an air brush. . A normal hand held gun such as C-47's Sampson with a 3 mmm nozzle ( a suction type gun) needs around 100psi the more pressure the better and about 12 -15 cfm minimum and its only a toy allowing an area only abouy 6-8mm as it spreads out from the nozzle as you have to hold it close so as not to loose the energy of the grit.

An industrial sandblasting gun in a small cabinet such as is available for home use needs even more capacity and pressure, 120 psi and the orifice size is usually only 3-4mm. These systems drop the grit through a hole about 5mm into a pipe about 15mm which then carries the grit to the gun mixed with air.

If the unit is working properly you only need to adjust the distance of the gun from the work to control the amount of material removed.

I have just seen that while I was writing this you have posted some photo's and I can see it is a gravity feed gun and 7cfm ( so it says)

As the air passes the grit being dropped into the air stream it is meant to take it out the nozzle, if you restrict it too much the air will blow the grit back up into the container. It obviously is supposed to work but to my way of thinking it is not much of a system (sorry).

Having said that have you tried to crush the granuals up into a smaller size or use any other grit? I think your Bicarb soda may be too light in weight to drop into the air where glass or other grits would be heavier and do so.

[Sterob]

Sterob,


As the air passes the grit being dropped into the air stream it is meant to take it out the nozzle, if you restrict it too much the air will blow the grit back up into the container. It obviously is supposed to work but to my way of thinking it is not much of a system (sorry).

Having said that have you tried to crush the granuals up into a smaller size or use any other grit? I think your Bicarb soda may be too light in weight to drop into the air where glass or other grits would be heavier and do so.

I originally used the cooking bicarb like you get from Coles, but it is very fine ( almost talcum powder consistency) and did not work very well.. The stuff I have now is 'granuated' and is designed for soda blasting. It can't be crushed any more and, would not work at all , even if I could. From what I've read, soda blasting works by making the granules 'explode' when they hit the part being cleaned. This is what does the work. I agree, heavier granuales would be better.
I've seen a product called 'Natrium 260' which has granules of 0.26 mm which seems to be the best, but AFAIK, it is not available here in Australia.
Maybe as my granules are so small, this requires alot higher pressure( to get more energy into the media) which I just can't achieve.

[tomhowell]

I don't have a lot to contribute to soda blasting.

All I can say is that when I last did soda blasting it was at work.
I work for a large company that manufactures & refurbishes all types of rolling stock (that's trains to us simple folk).

I was using a process named Acustrip to clean grime & graffiti off polished Stainless Steel passenger train sliding doors.

It was a wet process & used ENORMOUS amounts of compressed air.
I can't tell you about the flow volumes or the operating pressures but I can tell you that the compressor I was working from was the size of a Van & the hose was thicker than my frikkin arm.

The system used a safety trigger system that you had to grip REALLY firmly to get going.
It also had a gentle soft start arrangement so skinny stringy apprentices didn't get literally lifted off the ground on startup & whizzed around the yard like wile cyote at the end of a huge angry soda blasting nozzle.

There were three hoses which went into the nozzle.
Air ( the huge black python of a hose), Water about garden hose size, & soda maybe a bit bigger than garden hose.
These all fed into the nozzle & like I said, angry soda blasting happend out the end of the nozzle.

I'm thinking the soda was conveyed a fair distance to the nozzle in a wet state.
Really not sure, but it went about 20 metres from the hopper to the nozzle.
The soda, which I often had to hose off the doors after blasting was extremely fine icing sugar sort of consistency.

It all came together well though & cleaned the doors up a treat where nothing else would.
No such thing as paint that can take soda blasting.

The effect is great, really nice finish & happened double quick too.
It had an effective "patch" of area that was about 150mm wide or so at about 1 metre distance from the door.

Why not go suss out a professional set up & see what you can learn from those who do this stuff for a living.
Get some thing blasted by them & pick the brains of the operator & manager while they do your stuff.

have a blast!!!!


Tom:2tsup:

[Sterob]

"angry soda blasting"
I like that....lol
Yeah, that certainly sounds like a serious process....way out of my league.....:oo:
I was going to go and pick the brains of a business, but the only one I know about is about 180 km away.
I have approached a local sand blasting business and gave him my bucket of soda and asked him to have a go. He hasn't used it before but will give it a go and I will go and see the results tomorrow. Maybe they will start using it and make some money out of it?...we will see.

[Sterob]

I got my parts back today and generally, the results are good. Not perfect but not bad.
I took a couple of pics but the hubs are still wet so probably look better than what they are. The hubs are 'clean' but I didn't get the sheen I was after.
The guy who did it wasn't in when I picked up the parts so I couldn't pick his brains about how it when. He did say yesterday, that the smaller blaster was at another site so he would have to use the large unit. I think it was too large....lol

[Sterob]

I had another go at blasting again.
I drilled the tip I made in 0.5 mm steps until the gun began working again and it seems to work quite a bit better than with the original tip. The 'new' tip started off at 3.0mm and is now 4.5 mm. MAybe that is just larger than the venturi size, like someone here mentioned? The 'original' tip size was 6.5mm.
Afer I had got the gun working, I accidentally blasted my hand and it hurt like buggery! (It has never hurt like that before) so I assume the velocity of the medium now is alot higher , due to the smaller tip diameter.
Also I can see that the Bicarb is disintegrating after it hits the metal, so it's doing what its supposed to do to work.
Quite encouraging really.

[C-47]

Sounds like you are on the right track there and getting good results.
All the best.

[pipeclay]

I had another go at blasting again.
I drilled the tip I made in 0.5 mm steps until the gun began working again and it seems to work quite a bit better than with the original tip. The 'new' tip started off at 3.0mm and is now 4.5 mm. MAybe that is just larger than the venturi size, like someone here mentioned? The 'original' tip size was 6.5mm.
Afer I had got the gun working, I accidentally blasted my hand and it hurt like buggery! (It has never hurt like that before) so I assume the velocity of the medium now is alot higher , due to the smaller tip diameter.
Also I can see that the Bicarb is disintegrating after it hits the metal, so it's doing what its supposed to do to work.
Quite encouraging really.
just wondering how often do you blast your hand?

[Sterob]

just wondering how often do you blast your hand?

Only when it needs doing......

[llllmikellll]

This is quite interesting since Im just in the process of doing the same thing.
Ive got the sand working very nicely and was about to look for some soda to try.
Sterob, where do you get the soda for this type of work?

Cheers,
Mike

[Sterob]

This is quite interesting since Im just in the process of doing the same thing.
Ive got the sand working very nicely and was about to look for some soda to try.
Sterob, where do you get the soda for this type of work?

Cheers,
Mike

I got mine from a Paint Supply shop, of all things. They seem to supply all the things panel beaters and contract painters would want. A local industrial sand blasting business told me about them. I wouldn't have thought you'd have a problem finding some in Melbourne.
It came in a 25 kg bag and cost about $65. You want the granulated bicarb soda, not the fine powder. The bigger the chunks, the more effective it is.

[Woodlee]

I got mine from a Paint Supply shop, of all things. They seem to supply all the things panel beaters and contract painters would want. A local industrial sand blasting business told me about them. I wouldn't have thought you'd have a problem finding some in Melbourne.
It came in a 25 kg bag and cost about $65. You want the granulated bicarb soda, not the fine powder. The bigger the chunks, the more effective it is.



From what I've been led to beleive sawdust is also a good blasting medium capable of a very highly polished finish.I've never tried it myself .
I have seen the results of metal parts (washers)tumbled in saw dust in a wooden lined drum and they had a very highly polished finish.

Kev

[Sterob]

From what I've been led to beleive sawdust is also a good blasting medium capable of a very highly polished finish.I've never tried it myself .
I have seen the results of metal parts (washers)tumbled in saw dust in a wooden lined drum and they had a very highly polished finish.

Kev


Hmmm...never heard of that before....I've heard of using Walnut shells, but have not seen the results in the flesh.

[llllmikellll]

I wonder if the sawdust was just a carrier for some finer polishing medium.

[Woodlee]

I wonder if the sawdust was just a carrier for some finer polishing medium.



Not sure it was many years ago when I was an apprentice at Simpson Pope, all the washers and fidldy bits were put into hexagonal shaped drums and loaded with saw dust and tumbled for a few of hours .I think the saw dust removed the oil and polished at the same time.

A bit off topic ,when I worked in the local power station which had gas turbine engines ,we cleaned the turbine compressor blades by feeding peanut shells and or rice husks in to the air intake ,while the engine was running at half speed .

[davenkellie]

what brand is the granulated bicarb soda please?or does anybody know where to locate it in brisbane?i want to try it with air compressor and the cooking stuff isnt working!

[Sterob]

Hi DAvenkellie,
The only stuff I could find was the pic below. I got it from a an automotive paint supplier. About $50 for 25kg.It works quite well, but the velocity of the medium must be very high otherwise the granules will not disintegrate. The disintegration is what does the cleaning. If it just bounces off, its not working.
I had to make a nozzle for my gun with a smaller hole in order to get the velocity up high enough for the pressure I was using. The original size was around 8mm and I dropped it down to about 4.5mm and the process came alive! You will have to experiment with the size. I went to about 3mm and when up in 0.5 mm increments and stopped at 4.5mm. It might be better at a higher size, but I was not game to go any higher as if I was wrong, i'd have to make another nozzle...
This material is not as coarse as I would have wanted but, ya take what ya can get.....:D
The brand I have seen on overseas websites is called 'Natrium 260' and I think the '260' refers to the granule size.
Have fun.

[prozac]

Woodlee the Royal Navy use walnut shells to clean the turbine blades on their gas turbines propulsion units.

prozac

[hux]

Gents

When cleaning ammunition cases ie rifle and pistol cases prior to reloading you use either crushed walnut shell or corn cob media in a rotary tumbler.

Unless I saw the size of the bi carb granules I wouldn't be able to say whether the sizes are comparable. It is quite a bit more expensive though but when tumbling it lasts a fair while compared to say belting it out of a blaster at high speed.

[smoogs]

Hi DAvenkellie,
The only stuff I could find was the pic below. I got it from a an automotive paint supplier. About $50 for 25kg.It works quite well, but the velocity of the medium must be very high otherwise the granules will not disintegrate. The disintegration is what does the cleaning. If it just bounces off, its not working.
I had to make a nozzle for my gun with a smaller hole in order to get the velocity up high enough for the pressure I was using. The original size was around 8mm and I dropped it down to about 4.5mm and the process came alive! You will have to experiment with the size. I went to about 3mm and when up in 0.5 mm increments and stopped at 4.5mm. It might be better at a higher size, but I was not game to go any higher as if I was wrong, i'd have to make another nozzle...
This material is not as coarse as I would have wanted but, ya take what ya can get.....:D
The brand I have seen on overseas websites is called 'Natrium 260' and I think the '260' refers to the granule size.
Have fun.
Hi All. I have seen soda blasting and have had soda blasting done many times. Would get it done everytime. I have been dealing with a few companies. 1 www.asbsupplies.com (http://www.asbsupplies.com) THese guys also sell the stuff called bump soda and is water resistant, amazing stuff, you have to see it to believe it. Also sell small and large machines. THing i liked about it was ALL AUSTRALIAN........none of this overseas stuff. They make it here. ANother is called imperial soda blasting in newcastle. Great guy and knows his stuff.

[flmath]

Try this mob if you are in the Brisbane area.

http://users.bigpond.com/sodastrip/contact.html

:2tsup: