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Getting down to the Nuts & Bolts of blasting

The equipment required for sandblasting is really pretty basic: an air compressor, a container for the abrasive and a nozzle. There are, however, more than a few variables involved with these three elements! I'll briefly cover them here which should be enough to get you going if you?re interested in trying this art yourself.

The compressor

The compressor provides the air that operates your sandblaster. You will find a variety of them on the market and the choice can be quite boggling. I've tried several and will make a few suggestions to help you in selecting one that will meet your needs.

Air compressors are rated by CFM @ PSI. That's Cubic Feet per Minute at Pounds per Square Inch. That may not mean much to you and that's OK, just look for the rating number and stay above 6CFM @ 100 PSI free air. You may find a couple different ratings for a compressor. It may say it's rated at 7.6 CFM, but you need to look for the "free air" rating, which, at 7.6 CFM would only be about 4.9 CFM @ 100 PSI free air. To stay in the range you need to sandblast with any efficiency, you should be looking at nothing less than a 3 HP compressor. Currently I'm using a 5HP that delivers 9.0 CFM @ 100 PSI free air, which is rated at 15.4 CFM. Confused yet? All in all, you can expect to pay between $250 (left) and $1,200 (right) for your compressor.

Tank Size

The second compressor consideration is the size of the tank. The larger the tank, the less the compressor has to run to fill it up. It's not necessarily good to have the compressor running all the time - that's a sign that you're not getting all the air you require. I started with a 20 gallon tank, and the compressor ran quite frequently. I moved up to a 30 gallon and the compressor runs about a third of the time. Finally I gave up and went to the 85 gallon (above, right) as I was blasting several hours at a time and needed all the air capacity I could get.

Filters

One thing to be very careful about is the air filter on the compressor. I learned this the hard way by blowing one out of the water. My abrasive got into the motor and literally chewed it to pieces. My next compressor had an industrial, metal contained cartridge filter. You need to keep the compressor as far away from your work as you can. In another room is ideal but not always possible. But at least try and route the intake to another location (or outside) to be safe.

Avoiding Moisture

All you need is a length of hose to get to your job and you're set. Ah, another detail! Keep the hose as short as possible for two reasons. First, the longer the hose, the greater the drop in air pressure from your compressor to your work. Secondly, the longer the hose, the more opportunity for picking up unwanted moisture which can wreak havoc with your abrasives!
And speaking of moisture, it's a necessary task that when you're done with a job, release the pressure from the tank through the release valve under the tank. This will blow out any standing water that gathers in the tank. Another necessity is a water filter for the hose line. Many compressors have one at the tank which is nice, but remember your hose is also collecting moisture. Depending on the equipment you use to sandblast, move the water filter as close to your working end as possible.

Voltage

Before we move off of compressors, I should share with you that the larger ones will usually run off of 220 volts. Not a nice surprise to discover as you are unpacking your new toy. So be prepared. Some of the small compressors can be rewired to run off 110 volts, but I'd shy away from this lower end compressor. They can work fine depending on what you want to do, but I insist on a good, high pressure air flow and lower end compressors don't always provide that.

Gas Compressors

If just by chance you happen to have an old gas compressor out behind the barn, remember that a gas compressor only puts out about 60% of the CFM that an electric compressor does. So don't think because you have a 5HP gas compressor it is equivalent to the electric model - it will only rate comparably to about a 3HP electric.

Sandblasting Systems

There are basically two types of sandblasters, siphon feed and pressure pot. They work much like their names. The siphon feed pulls the abrasive from the container using suction power that is created in the sandblasting gun itself. Air is passed over the hose end that leads to the abrasive, creating a suction, and then the abrasive is mixed with the air and sprayed out the nozzle.

Differences

The pressure pot works a little differently. Here the abrasive is put under pressure and forced out of the container in a controlled flow and mixed with the air at that point to force it up the hose and out the nozzle.
The basic difference is in the pressure with which the abrasive leaves the nozzle and its impact on your target. The pressure pot, working under far less pressure than the siphon method, produces much greater pressure at the nozzle. You might achieve the same pressure results with a pressure pot at 10 PSI as you would a siphon process at 85 PSI. Big difference!

You might also notice the difference in the nozzles between the two. I find the gun type much easier to handle than the straight nozzle. I use both depending on the project and how much pressure I will need.

Nozzles

Both nozzles have ceramic tips. This reduces static and extends wear. Ceramic does wear down and loses its ability to constrain and direct the flow of abrasive. In either case, you can get many hours of use before having to replace them.

Gun Types

Here are two types of blasting guns. The one on the left I use with my siphon system. Notice that it has two hoses running into it; one for abrasive and the other for air. You can pick them up from most hardware stores for about $40 including the hoses and pickup tubes that go into the abrasive.

The gun in the middle is a PAB blasting gun. It replaced my small airbrush pencil type gun. It comes in two feed hose sizes, 1/4" and 1/8" and a variety of nozzles for both. Works like a champ - I love it. This has a carbide nozzle that wears about 10 times as long as the ceramic and costs a bit more too. I have even carved designs in light bulbs! Why you might ask? What else do you do with burnt out light bulbs? Check my suppliers page for more info on the PAB gun.

The gun (nozzle) on the right is the standard that comes with many sandblasting setups. I use it all the time, it's a great work horse. Both of these last two guns only have one hose, thus they run off the pressure pot and the hose carries the abrasive under pressure from the pressure pot.


Prices

Price wise, you can find siphon systems from$30 to $60 depending on volume and I built my own for $5 and a few scraps around the garage. I used a copper fitting to come out the bottom of the bucket and I added a couple very small holes to allow air to mix with the abrasive before it begins its trip up the hose. By covering or opening the holes you control the amount of abrasive that is sent out the nozzle.

The pressure pots are a different story. They will run from about $80 on up. They hold around 10 pounds of abrasive at the smaller end and withstand up to about 100 PSI - just in case you want to blow a hole through the foundation of your house! For my own use, I have two 40 pound capacity tanks and I end up refilling them more often than I care to.