Disclaimer
Please do not contact me to ask for more specific info about how to anodize yourself. I will probably just ignore you. I have provided this article as an informative guide. It is not, nor wil it ever be my intention to encourage you to try this at home. In fact, I forbid you to do it. Really! The chemicals used are nasty, and mixing them up in the wrong way makes them deadly even. Therefor I intentionally left out some uninteresting but crucial steps and details. All I want is everyone to understand what anodizing really is, and to give you a grasp of how its done, because i know a lot of people have no idea.Aluminium
Most of modern ‘metal’ yoyos are made from aluminium. Aluminium is commonly used in the industry because of its good specifications. It’s lightweight and easy to machine, whilst still maintaining satisfying strength properties. Moreover, it’s relatively cheap. Other metals used in the yoyo industry, like titanium, offer only slightly better specifications at a much greater cost.
However, to enhance the properties of aluminium, it is commonly alloyed with other metals. The International Alloy Designation System is the most widely accepted naming and classification scheme for these alloys. Each one is given a four-digit number, where the first digit indicates the major alloying element(s). In yoyo industry, 6061 and 7075 are the most well-known, but there are tons more for various uses.
An overview:
In addition, these alloys can also be treated to obtain even more specific properties. These treatments also have codes assigned to them. So if you see 6061-T6 for example, that means the 6061 alloy has been heat treated and artificially aged. There’s a lot more of these, but I’m not going to get into that here.
Prepping
Beadblasting
Beadblasting is a specific form of mediablasting. There are lots of different names for the basic process (usually derived from the media that is used to blast), but they all boil down to the same principle. An abrasive granular media is blasted at high speed onto a surface to clean it up. Due to the high-velocity impact of the particles, old coatings (paint, anodize, ...) can be blasted right off, ending up with up a nice rough surface structure, perfect for grinds because of a smaller friction area.
Although beads are the media commonly used for ‘soft’ aluminium yoyo surfaces, I will refer to the technique as mediablasting from now on. Just to remind you that there is a wide range of other media, such as sand, walnut shell grains, glass particles, soda, metal billets, ... Each with their own applications. To blast hard surfaces, a harder media is used. To blast softer surfaces, a soft media is used. Duh! As far as I know, everything can be mediablasted. You could even blast your eyelids if you wanted to, but I don’t recommend it.
To get the particles to hit your piece at high enough speeds, we usually make use of compressed air. In some applications, pressurized water can also be used, but as metal and water don’t get along all that much, this technique is nowhere near as popular as dry blasting with compressed air. A physics law, called the Bernouilli-effect, enables the media to be automatically suctioned into the nozzle through a hose (the purple one on the graphic). It is injected in the air stream, and blasts out the nozzle at high speed.
The setup depicted above is the most basic one, found in most DIY workshops. Know that there are more advanced (and expensive) systems out there, often used to strip large car parts and panels, but as I intent to use it only on small yoyo parts, this is a satisfactory setup for my needs. However, to be able to mediablast in a comfortable way, not any compressor is suitable. You need a large air flow at a high pressure, so a cheapo system may fail very fast. Apart from that, a sealed blasting cabinet is certainly not a bad idea, as the media tends to fly all over the place. Not only can you work without having to scratch the sand out of your buttcrack every five minutes (believe me, I’m not exaggerating ...), it also allows you to recuperate your media to use it again later on.
Etching
Etching is the chemical counterpart of mediablasting I guess. The piece is placed in a tank with an aggressive chemical agent, which eats away the top surface area, and leaves a somewhat ‘satined’ surface. It’s not as rough as a mediablast surface though.
As with mediablasting, the pieces cannot be exposed for too long, or it will start to change dimensions too much. Because this is a reaction between aluminium and the chemical bath, paint or other finishes like teflon coatings will not respond too well in the chemical bath, as they form an insulating layer between the metal and the liquid.
After etching, most professional companies go through an additional step called ‘desmutting’. I don’t do it, but it is some kind of last cleaning bath before anodizing.
Polishing
As smooth as a metal surface may look, usually it is still quite rough on a microscopic level. Polishing is a simple and cheap process by which you try to get the surface so smooth, it has an almost mirror-like finish. This can be done through sanding the piece with very fine sand paper, followed by excessive rubbing with a piece of cloth of some sort. There are polishing products on the market you can dip your cloth in, to get the best results.
Satining
In opposition to a polished look, many people prefer satining their yoyos. This can be done in an even easier way by just sanding the surface to a desired look. The difference between satining and etching/mediablasting, consists of the fact that satining is achieved by manual strokes, which are ultimately visible in the end result. So we could use this fact to our advantage to achieve unique looks, like a ‘spiral satin’ for example. Mediablasting or etching on the contrary always give a perfectly even end result.
Polishing/satining is something I don’t provide as a service, as I don’t like doing it, and because I think everybody can easily do it him/herself before sending their yoyos to me.
You can see a comparison diagram below. It represents a magnified cross-section of the metal surface through the different techniques.
Anodizing
Misconceptions
A lot of people have a very faulty image of what anodizing really is. So here is a short list of the major misconceptions I read on the forums.- Anodizing is not like painting. Its not a layer put onto the surface. It is a layer that is electrochemically formed within the surface. So basically the original surface is altered.
- The anodized layer has an average thickness about 25 microns. The human eye is unable to detect a difference this small, so as a result, anodizing itself does not affect the look of your yoyo. A scratch/ding, however shallow, will show after anodizing. Always. It may be less visible due to the application of colors, but it will still be there just the same.
- Anodizing is colorless. We usually talk about anodizing as a color layer. Well, simple anodizing only alters the composition of the surface, and does hereby not add color. However, slight tint changes are possible depending on the alloy type. Coloring is an optional step, used when aesthetics are important.
- Not all metals can be anodized. Aluminium and titanium are anodized abundantly in the industry, but other metals that will also take anodize are magnesium, zinc, ... Steel is an example of a metal unfit for anodizing. So forget about your CU, St. Eel, ... Also, since you have to put your part in an acid bath for about an hour, it is usually not a good idea to try anodizing metals that will be corroded by the acid ... Note that not all aluminium alloys are equally good anodizing candidates as well.
What is it
Anodizing is the formation of a layer of oxide on the surface of an aluminum piece, using a bath of dilute sulfuric acid as an electrolyte, by charging the piece electrically. This is where the name comes from: the piece being anodized is attached to the positively-charged pole of the electrical circuit (i.e. the anode). A second large lead or aluminium plate is usually also immersed in the electrolyte, which becomes the negative ground pole (i.e. the cathode).
So what does anodizing actually do? Well, the electrical charge and mild acid oxidize the surface of the aluminum, forming microscopic crystals of aluminum oxide. This oxide surface is very hard, much harder than the base material, but very thin, usually averaging at about 25 microns (0,001 inch). The anodic layer on yoyo’s is one of moderate thickness. This is known as Type II anodizing. There are other types, which I won’t discuss here as they are not as interesting for a yoyo finish. The layer as a side effect also becomes porous and can now take on pigment if needed.
The anodic layer can (and usually will) change the dimensions of the part being anodized. The addition of oxygen to the surface layer makes it thicker, usually adding a few microns thickness to the surface. This doesn’t sound like much, but it can make a difference in some tight fitting pieces. While most aluminium alloys average around 35 to 40 on the Rockwell C (hardness) scale, the oxide layer is closer to 52 to 55. The anodizing prevents further oxidation, so the piece wont rust or corrode any further, and also makes the surface much more wear and scratch resistant.
Techniques
Industrial anodizers do not offer much flexibility. Machine parts need only good mechanical properties, so the aesthetic part is usually limited to a few solid color choices. Also their services are maily focused on huge runs.
Luckily, some companies do specialize in the aesthetic aspect as well, with their main applications in the paintball gun, yoyo and crossbow scenes. Gruntbull being the most well-known among the yoyo community. There’s also 125customs, and, well… me.
So what techniques are there? Although the above mentioned companies offer far more possibilities in techniques and colors, there are only so much techniques that are feasible from a commercial point of view. Basically, the more labor intensive, the more it will cost you.
An overview:- Fade: This technique is easily achieved by dyeing the part in the lightest color, followed by dipping part of the surface in the darker color until you get the desired look.
As seen on: M1, Project. - Splash: Mass-introduced on yoyos by CLYW, now abundantly used by other companies as well.
Usually a mask of rubber cement is dripped all over the surface, possibly with a first color already applied. After drying, the color is bleached off and the second color is applied. After sealing, the mask is removed and you got yourself a nice splash design.
As seen on: BVM, Peak, Hectic, DNA, ... - Acid wash: This effect is achieved by applying bleach on a colored but still wet surface. The bleach spreads out unevenly and after applying a second color, you get a very unique look. Another possibility is letting the surface dry and then treating it with bleach. This gives more defined edges between colors. This technique is often referred to as sponge acid wash.
As seen on: recent CLYW stuff, ... - Masking: Simple logos, lettering or a combination thereof can be cut out on stickers and masked off in order to get the design reproduced in the anodized layer.
As seen on: my custom stuff.
There are off course lots more possibilities. As with everything, the only limit is your own imagination, but you have to find somebody than can and wants to do it. Some random examples: maple drip, swirl ano, speckle dust, ...
Dyeing
Anodizing is by definition used to enhance surface properties of mechanical parts. The fact it is now porous and able to take on color pigments is just a fortunate side effect. Nevertheless, it is so easy to do that it has almost become an elemental part of the anodizing process. A piece can be anodized, and not dyed, but it cannot be dyed without anodizing.
There are commercial pigments out there, but DIY setups usually use fabric dyes like RIT or Dylon for obvious reasons: they are cheap, easily available, you get lots of color choices, and in my experience, they do the job perfectly. It usually takes about 10-15 minutes of soaking your part in the dye tank to achieve perfect saturation.
Sealing
The last step of the anodizing process is to seal the color pigments into the metal surface. This can easily be achieved by suspending your part over boiling water and let the steam do its magic, or just by putting it in the water itself. I usually suspend it first for a while because if you put it into the water immediately, some of the pigment gets lost.
The sealing process, because of the porosity of the oxide, hydrates the crystalline layer, which swells the oxide, closing the pores, sealing the dye within. Because the layer is so thin, the dye must be heavily concentrated, and even then, the color will be somewhat translucent. This is what gives the color anodizing its characteristic metallic sheen; the shiny base aluminum shows through the color. Because of this semi-transparency, the piece cannot be anodized white; the aluminum would show through, giving a light grey color.
By default, I boil for at least 10 to 15 minutes. You don’t want to spend hours on a sick design, and then accidentally rub it off because you didn’t seal well.
So, there you have it. A perfectly finished yoyo. Thanks for reading all the way down. Hope you learned something in the process.