Whenever I begin with a student, I generally take him or her to the blaster, hand over a piece of glass with a few shapes already cut and pulled in the protective vinyl resist and say, “Let’s see what you can do.” This is my way of seeing just what the person knows, and what he or she is capable of. It usually takes about 30 seconds and goes about like this: (If any of you ever becomes my student, you’ll pass this test with flying colors). The student, who shall be named Sandy, accepts the glass, opens the cabinet door, leans the glass against the back wall, aims the hose, and fires away. Sandy has already failed.
What has Sandy done wrong, other than subjecting himself to this abuse in the first place? The first, and most major crime committed was not looking to see what size nozzle is on the end of the blasting hose. And the second was not checking the pressure at which he was blasting. Maybe students are too trusting and feel that I would always provide them with the proper set of circumstances. However, I never put my size-seven track shoe on the foot pedal without checking those two things. It is so deeply ingrained. Before I step on the foot pedal and restart the flow of grit, I look at the aperture of the nozzle and the pressure gauge, even if I’ve only stopped to make a few pulls, knowing full well that leprechauns did not sneak in and change anything.
As the title of this article suggests, the nozzle, or more precisely the size of the opening of the nozzle, is something that must never be taken for granted when blasting. There is a vital relationship between nozzle-opening size and pressure, two factors which will affect the distance from the nozzle opening to the shape to be blasted, as well as the speed at which you blast. If you think about it, this relationship is simple: the smaller the nozzle opening, the faster the grit moves. A simple analogy is water spilling out of a hose. Stick your thumb over the end of the hose, effectively making the opening much smaller, and the water will shoot out. Same amount of water, at the same pressure leaving the spigot, but it moves much faster and farther. The same is true for a sandblasting nozzle. When it is brand new and the opening is small, the grit comes out of it faster, with a lot more cutting power. As you use the nozzle, and the abrasive eats away at the sides, the hole grows larger. The same amount of grit will come out of it, but now it is spread over a wider area.
Let’s see how the size of the nozzle opening correlates to how we sandblast. When carving, if you wish to achieve a smooth, rounded shape, the epicenter of your blast must fit well within the confines of the exposed area. This insures that the center is deeper than the sides. Therefore, if your shape is narrow, the orifice of your nozzle must be small. If you use a nozzle with an expanded orifice and put too much distance between your hose and the glass, you cannot possibly remain within the confines of the shape.
This results in multiple problems; your carving may be deep, but also flat and boring. The other problem is that the surface area of the blast is so great that it hits and alters any exposed surrounding shapes, often blurring what should be sharp, defining boundary lines into soft, marshmallowy blobs. What casts those beautiful shadows in a well-carved piece is the sharpness of the lines between shapes, not necessarily the depth itself. You want the stream of grit to be precise enough to fit directly inside the shape you are carving, and for that, you need the properly sized nozzle opening.
Now that you understand the importance of orifice size and distance, let’s consider the different types of nozzles. The first thing to consider is the starting orifice size. Most non-industrial sandblasting set-ups use a 1 5/16" long nozzle, a size most would consider standard. There are a host of aperture sizes available for these nozzles; but, if you’ve been paying attention, you’ll understand why I only invest in the smallest openings. I buy nozzles with 1/16" apertures since the more you use them, the larger the orifice becomes. The sandblasting process will quickly provide you with ample larger openings for surface etching jobs, and when they become even larger, they’re great for shading or light frosting (Figure 1). It’s a waste of money to buy nozzles with already large orifices.
Nozzles are most commonly created from two materials, either ceramic or tungsten carbide (Figure 2). Ceramic nozzles are lighter and have a tendency to get blown out much more quickly than their heavyweight cousin, the tungsten carbide. I used to do so much fine work that I preferred the ceramic nozzles, since their light weight allowed me such ease of handling when working in teeny shapes. I found it difficult when doing limited editions of Warner Bros.
Grinch, for example, to use them interchangeably. There was a definite difference in my shaping abilities that I couldn’t justify in the finished product.
I really love the ceramic nozzle and in the past used it exclusively, and here’s why. A ceramic nozzle used to cost fewer than two bucks as opposed to the hefty $20 price tag attached to the tungsten carbide nozzle. What you had for $20 was either one nozzle whose orifice got slowly larger or 10 nozzles that would undoubtedly wear out faster, but would provide you with 10 nozzles of varying sizes for different applications.
But, like everything else, this has changed. Now, for various reasons, a 1/16" ceramic nozzle from Leitch and Co., in Oakland, CA, sells for $6, compared to the tungsten carbide model, which has only appreciated to about $26 a piece. Now it’s more like a 4 to 1 ratio, and the ceramic nozzles no longer offer enough blasting time with the smaller orifices. Even with the unfavorable ratio, I am a creature of habit, and continue to love the ceramic nozzle. Herb, at
Glastar, has persisted in his quest to provide me with the 1/16" ceramic, and now offers them (hallelujah) at a dozen price of $55 or 5.50 per nozzle, 50 cents off the individual price at Leitch & Co, or two free if you order a dozen. Such a deal.
If you’re just beginning your blasting career and your bucks are limited, I suggest a dozen of the ceramics and one or two of the tungsten carbides, until you get the feel of each. Then you’ll have a bunch for all types of jobs. Hopefully, you will quickly earn so much money blasting, that if you so choose, you can order a dozen tungsten carbides and catch a significant price break. I keep both on hand. If I have a job that’s going to keep me blasting for a day or two, I grab a tungsten carbide. If I have a small but complex job, I use a ceramic. It’s a matter of personal choice, and over time you will make your own decision. One thing I won’t ever do again, however, is switch in midstream.
One last thing before we move on. Remember, it is rare that I use the same size nozzle within a given project. There will be small shapes to carve, larger shapes to carve, areas to solid frost, and possibly sections to be shaded. Take a few seconds and use the proper orifice size for each facet of the piece. Your work will reflect the care and diligence you practice. It is not uncommon for me to have five different nozzles on standby. Start thinking about what you’re blasting and take a look at that nozzle. You’ll be glad you did.
Now for the big guy. We go from the 1 5/16" nozzle for smaller pieces to the macho 3 3/4" hunk for more commercial applications. I have encountered people who didn’t know that these larger nozzles even existed. Just as a too-large nozzle opening can make your work look dull, a too-small opening can mean that a large job can take forever. I do a lot of residential and commercial work, and some of it is huge. It’s just not practical to attempt to solid frost a 5' x 10' piece of glass with a small nozzle. Although these big nozzles come with different orifice sizes, I get the smallest, 3/32", since it too will get bigger with use, and it may be used for different applications. I have done mermaids, human figures, complex designs, and any number of things up to 8' tall, and had I used a small nozzle I’d still be blasting. The same combinations of carving, solid frosting, and shading apply to big designs as well as small, so hang on to your used nozzles. You’ll need them. And as a final thought, while you will obviously need different end-caps for the 1 5/16" and 3 3/4" nozzles (Figure 3), you don’t need a separate light air-hose assembly for both nozzles. All you need is a reducer to couple the large end-cap to the hose end (Figure 4).
I hope this article has given you food for thought. If you’re a regular reader, you know I’m a fanatic for the proper tool for the job. I can’t believe the number of studios I’ve visited that are using nozzles with orifices as big as your average shotgun barrel. Often it’s the little things that matter. Perhaps you have really worked hard on your blasting and yet notice something is not quite right; it’s not quite as crisp as you would like, or the shapes are flat. Check your nozzle. It could be that simple.
Nozzletov! Just a little note here: Our new book, TRUE GRIT: Unraveling the Mysteries of Sandblasting, has been released and is available. Call for info. We even pay you a dollar to let us autograph it. See, you make money on the deal. Until next time- remember, Grit Happens.
Butch Young has been a glass artist for over 10 years and has carved glass for artists as diverse as Chuck Jones,
R.C. Gorman, Erte, Tsing, Robert Lynn Nelson, John Lennon, Donna Howell Sickles, Andrea Smith, Laurel Burch and Eileen
Borgeson. Her work is in galleries and private collections all over the world. She teaches advanced glass carving at her studio in central New Mexico. For a reasonable consulting fee, she can critique and help strategize your work in order to woo an artist. She can be reached between 8 a.m. and 5 p.m. Mountain Time at (505) 861-3328. She does not answer the phone during Jeopardy or Dallas Cowboy football games. Check your local listings. |
