Biroza, more commonly known as rosin is a gum resin which is applied to the hairs of musical bows which facilitates the bowing of the string. In this page we will look at it from the standpoint of Indian bowed instruments such as sarangis, dilrubas and esrajs. However since these rosins are almost always formulated for Western instruments such as the violin, numerous non-Indian references are unavoidable.
Now I know that a lot of people have questions and concerns and wish me to get right to the khaas baat. So here is the abbreviated version:
Now this is really all that you need to know, but if you want more information read further.
Let us take a closer look at rosin.
The etymology of the English word "rosin" is interesting. Rosin is just a variant of the word resin. Although this is obvious, there has arisen a slightly different colour to the two terms. Where the English term "resin" has acquired a generic quality of referring to almost any gummy extract of a plant, the term rosin has acquired the implication of referring specifically to the refined material extracted from conifers (e.g. pine trees). In medieval English this was referred to as "recyn", "resyn", "rosyn", and "rosine". These terms were evidently derived from the middle-French "resine" and "resin". Both the middle English and middle-French terms were evidently derived from the Latin "resina".
The etymology of the Hindustani "biroza" is not clear. The term biroza (Urdu) is also called biroja (Hindi) and baroza (Punjabi). The term biroza has generic quality about it that seems to be applicable to almost any gum resin.
The making of rosin is interesting and has a long history. The earliest forms of rosin appeared to be nothing but the naturally weathered sap from pine trees. However for a long time, rosin has been a product of very sophisticated agricultural and industrial processes.
The process of making rosin actually begins with the pine trees. Sometimes live trees are tapped. Just as toddy palms are tapped to get shendi and maple trees are tapped to get the sap for maple syrup, in the same way pine trees are sometimes tapped to get their sap. However in many places the living trees are not tapped, but the entire trees are used. It is common practice to grind pine wood into pulp for the paper industry. In such situations, a mash of ground wood is heated in giant tanks known as "digesters"; these separate the wood pulp from the various oils found in the sap of the tree. It is from this liquid extract that rosin is often obtained.
After the saps have been collected, the finer versions of rosin are made by mixing the saps from various other trees; these may include larches, spruces and firs. The nature of these mixes are closely guarded secrets. These saps are then strained and heated. After they have been heated a while, the lighter turpentine is boiled away leaving the rosin behind.
The colour of the rosin will vary due to a number of reasons. One cause for variations in colour are the season in which the saps are tapped. When the saps are tapped in late winter or early spring, then the rosin tends to be hard and a have a golden colour. On the other hand if the saps are tapped in summer or fall then the rosin tends to be darker and gummier. Another reason for the colour to be different has to do with the manner in which the saps are heated. It is also common to add dyes to the rosin; this is generally to make the rosins more appealing to various markets. The consequence of adding dies to the rosin means that the colour of the rosin is not necessarily indicative of its characteristics.
It must be noted that a myriad of other ingredients may be added to rosin to alter its characteristics. Many times metals such as gold, silver, lead or copper are added to the rosin. It is said that this increases the friction. On other occasions substances like bees wax are also added to the mixture.
Although there are innumerable formulations of rosins, the various mixes tend to be divided into two classes for marketing reasons. There are the general purpose rosins, which are commonly used for violins, and there are the bass rosins. The violin rosins are harder and dryer while the bass rosins are generally softer and stickier.
It should also be noted that there are also hypoallergenic rosins for those who are unfortunate enough to be allergic to the dust from the rosin.
This is all well and good, but let us see what this has to do with the bowing of the instrument.
The physics of what goes on in the act of bowing and the effects of the rosin are interesting. At first they seem simple, but in practice there are a number of very complex theoretical and practical considerations.
In its simplest, the act of drawing a bow hair across a taught musical string may be described as a process of "grab and release". It works like this. The string is pulled laterally under the force of the friction exerted against the string. As the string moves laterally there is a gradual increase in tension. At some point this lateral tension becomes greater than the force of friction, at which point there is a sudden rebound on the part of the string.
This is where the rosin is important. If you have ever tied to push a box across a floor, you can feel that it is much easier to keep it moving than to start it. To put it another way, we can say that the resting coefficient of resistance is greater than the sliding coefficient. The purpose of the rosin is to accentuate this difference. But not every formulation of rosin does this in the same way.
The process of "grab and release" creates a sawtooth motion at the place where the string meets the bow. The acoustic consequences of this sawtooth motion are profound. It tends to cause the string to produce many more overtones than a vibrating string would normally tend to do.
At this point a lot of very complicated things happen. Some of these things happen with the string (e.g., Helmholtz motion, double-slip motions), some things happen with the skin, and some things happen with the cavity of the air inside the resonator. The complex resonance of the skin and air cavities are all very interesting, but they are actually tangential to the topic of the rosin, therefore we will not discuss them here. But the complex motion of the string is very significant.
The consequence of this unusual string motion is very profound. Although we will not go into details here, there is one thing that must be kept in mind. You must be constantly sensitive to this resonance and constantly adjust your bowing to be part of it. Never forget that the motion of the string influences the grab / release mechanism of the bow; at the same time that this grab / release motion influences the motion of the string.
We discusses bowing and rosin in great length, but as musicians we want to know the "bottom line". In other words, you want me to tell you to go out and buy "such and such" rosin and all will be right with the world. I hate to disappoint you, but it is just not going to happen.
The reasons that I cannot just recommend a particular brand, is that I do not know what you are playing. A sarangi with its gut strings will certainly behave differently from an esraj or dilruba with its metal strings. Even within dilruba / esraj applications, I do not know what your strings are, or what key you play from. I myself have two dilrubas and one esraj and they are all strung and tuned differently. I also do not know what bowing technique you are using (i,e, do you bow with the hair flat against the string or do you have it set at an angle). With these myriad of variables, there is no way that I can pontificate about what rosin you should be using.
However I have given a lot of information. I hope that this information will allow you to experiment with some clear concepts of what is going on. Intelligent experimentation is always better than just randomly going out and buying every rosin under the sun.
(OK, I know what you are thinking. You want to know what I use. I prefer a nice, sticky, bass rosin. I find that the light coloured, hard rosins like most violins use just does not allow me to get that rich, multi-textured sound that I like.)
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