A popular explanation of the 4BO camouflage pattern, which was used to paint Soviet armored vehicles and other equipment
Armored vehicles aren’t just the equipment itself, but also everything that surrounds them. So, interesting stories emerge not only about the vehicles themselves, but also about all sorts of related things. This includes, among other things, the specific paint schemes used on armored vehicles from different countries. If anyone thinks this was a simple matter, I’m afraid I have to disappoint them. Debates over the colors of armored vehicles often turn out to be fierce, and the arguments presented may be based on sources of questionable reliability.
There are various theories about exactly what the camouflage pattern looked like. The TT-26 from the “Patriot” collection is painted in that pattern, and a sample of the paint has been preserved on the tank.
Perhaps the most controversial color for armored vehicles is 4BO. Developed as a result of extensive scientific research, this paint was the standard for Red Army armored vehicles, remaining in use until the early 1950s. Debates about it continue unabated, and are unlikely to subside. In fact, people sometimes even try to find this very 4BO where it never existed. Trying to convince them otherwise is a futile endeavor, but it’s worth telling people who aren’t very familiar with this topic about 4BO—and explaining at the same time why the debates over “the one and only correct color” are pointless.
This is roughly what the 3B AU color (“emerald”) looked like; it was very similar to the German Feldgrau No. 3. It was phased out because the color was easily identifiable in aerial photographs.
So, to begin with, it’s worth briefly recounting the history leading up to the introduction of the 4BO. Originally, Red Army tanks were painted in the so-called “pea” color, similar to artillery. The vast majority of armored vehicles in the 1930s were painted in what was known as a “protective” color. In 1934, the Research Institute of Engineering Technology of the Red Army (NIIIT) was established, which focused, among other things, on paint. This is how the 3B AU paint came into being (very similar to the German RAL 6006; it is sometimes also referred to as “emerald”), which was essentially a Russian version of the German Feldgrau No. 3. This color, which was used not only on equipment but also to paint helmets, was rejected fairly quickly. It turned out that it was detectable in aerial photography.
The first steps toward 4BO were taken in 1937; the paint was tested for two years
Interestingly, as early as the beginning of January 1937, the NIIIT was working on another paint formula, which could not be deciphered. The main components of this paint were green chromium oxide (18–19%) and light ochre (73–75%). The result was a thick paste, which was then mixed with linseed oil. Experiments were conducted on the remaining components. Work was expedited in March 1938 by K.E. Voroshilov, but in practice, the first tests of what would later become 4BO began as early as the summer of 1938. Several paint formulations were tested, not only on tanks but also on artillery, as well as on wooden and metal surfaces.
4BO was put into service in 1939
Thus, in 1939, the very same 4BO paint was introduced. Its classic composition was as follows: dry Zhuravskaya ochre 51.5%, chromium oxide green 13.1%, Kron orange 5.3%, and natural linseed oil 30%. The paint was supplied as a thick paste, which was then thinned with linseed oil. As the 4BO theme evolved, a camouflage pattern was also developed, which is the subject of a separate article. And while the camouflage project dragged on, 4BO—as a vitally important paint (indecipherable, unlike 3B AU)—was put into use rather quickly. As early as 1939, the first factories began switching to it.
4BO for 1941
However, it’s not as simple as it might seem. First, some factories—especially artillery factories—never switched to Code 3B at all, continuing to use “protective” paint. Artillery factories switched to 4BO later than tank factories; “protective” paint may even have been used as late as 1941. Second, the color itself—which was, in a sense, the base color—was supposed to vary by region as early as 1939. Third, some factories applied 4BO over an iron-based red lead primer, some over a lead-based red lead primer, and some even applied two coats of 4BO. And such inconsistency existed even before 4BO; it’s no coincidence that those same BT tanks look somewhat lighter. Finally, 4BO was supplied as a thick paste, and the exact ratio in which it was mixed with linseed oil is a separate issue.
The artillerymen, by the way, had their own color. The guns and the tank might have differed
I’ll go even further: samples of this color vary slightly across different archives. Even within a single case file at the Central Archives of the Ministry of Defense of the Russian Federation (TsAMO), there are two variations of this color. And they’re quite dark. At the same time, color photos—even taking into account that AGFA color film had a tendency to shift toward red—show a slightly different color. And yes, different types of tanks can vary in shade. Thus, that very “Holy Grail” of display modelers and other scale modelers looks like a classic Schrodinger’s cat. Of course, you may have stumbled upon “that very 4BO,” but it pertains to a specific vehicle from a specific period.
German color photographs are quite distinctive in their color rendering
And that’s only half the problem with finding the “perfect 4BO.” The fact is that chromium oxide, which is responsible for the grass-green color, tends to gradually “fade.” For this reason, the base color gradually shifted toward a yellowish hue, which was imparted by Zhuravskaya ochre. That’s why excavated armor parts with their original paint often have the same shade that the paint would have taken on after prolonged use. Incidentally, it adheres well, but it also takes a long time to dry. At the same time, in the second half of the 1940s, there was a flurry of criticism directed at 4BO, specifically related to the paint’s rapid deterioration. Presumably, this refers to the aforementioned chromium oxide.
With the German ones, the colored film takes on a reddish tint. And it’s difficult to spot the machined parts, because the chromium oxide wears off.
The first attempt to replace 4BO with a different paint was made in 1949. At that time, Plant No. 183 began painting T-54 tanks with perchlorovinyl-based paints, as well as paints based on pentaphthalic resin. The switch to these paints became more widespread in 1952. Later, the perchlorovinyl-based paint became known as HV-518; it outlasted the Soviet Army and is still in use today. But… you might laugh, but they didn’t manage to phase out 4BO until the mid-1950s. In 1955, the Chelyabinsk Tractor Plant (ChTZ) was still producing T-10 heavy tanks, which continued to be painted with the “poor-quality” paint. The PHV-69 enamel, which was used in artillery, showed the best results in testing.
The Colors of American Film
So, there’s another point here that’s just as interesting. This is especially true for bench-modelers, who are usually the main source of the debate about “why is your 4BO so green?” The thing is, 4BO in its pure form simply isn’t suitable for bench modeling. A model painted with this paint will be too dark. In practice, this means the paint needs to be lightened slightly—which is exactly what some manufacturers do. And these are just conventions that largely strip the debate of any deeper meaning. Unless, of course, you’re arguing just for the sake of arguing.
The 4BO was widely used until the early 1950s
Another interesting point concerns certain misconceptions about the reality of “genuine 4BO” production. It’s all true; what’s more, the theory that they’ve supposedly stopped mining this type of ochre is shattered by harsh reality. The Zhuravsky Ochre Plant can only laugh at such claims—it mines ochre in commercial quantities. Anyone who needs it can easily mix their own paint—some for helmets, others for larger items—bypassing all those middlemen who sell little jars at astronomical prices. In short, if you’re planning to make your own real 4BO, it’s actually quite easy.
And in some places, even into the mid-1950s
But this is where the now-popular expression “you can, but why?” comes into play. Let’s say it’s more or less suitable for a helmet. But why on earth would you want to paint a tank or a cannon? No, no one’s stopping you. Just don’t be surprised later when your beautiful color turns yellowish from exposure to the sun and rain. And then you’ll have to repaint it. The only thing that’ll warm your heart in this case is that you painted it with “that very 4BO.” Here, as they say, we sing a song to the folly of the brave. But from here on out, think for yourselves: do you really need all this, or not?
The Museum of Russian Military History took the most sensible approach. They selected a color and made it the standard.
What should you do in this case? Everyone has to figure this out for themselves. At the Museum of Russian Military History, for example, they opted to use modern paint, which they then “refine” with linseed oil. The result is a very pleasing color that also holds up well. Don’t overlook the achievements of modern chemistry, especially if you need to paint something at a 1:1 scale. As for modelers… decide for yourselves what you consider to be the “Holy Grail.” I just want to say one thing. Attempting a scientific approach may lead to disappointment. Because you’ll find that when it comes to painting armored vehicles, “it’s not all that straightforward.”
List of Sources:
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- CAMO RF
- RGV
- RGAE
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