Bridge blanks are a practical necessity, as the rote (machine) work required to make a mass produced product (a blank) does not require the refined skills of the particular sort that actually carving a blank into a bridge does. Beyond that, there are issues as to the “tightness” of the wood grain and its degree of dryness that have an impact on sound quality. They also impact how difficult it is to work with the bridge, because the dryer, older blanks are harder to work on, but produce the best results in terms of sound and responsiveness. Hard, dense wood transmits sound faster, (hence the desire for tight-grained, old bridge blanks). A higher “arch” (longer “legs”) is achieved by cutting the top of the feet of the blank down from the top of the feet (and, to a degree, carving the arch higher), and the bottom of the feet must be fit to the top of the instrument. Longer “legs” means less wood, which translates into faster response, which is the main reason that Belgian bridges have become more popular; they have longer “legs” and less wood on top than the Aubert blanks. The thickness of the top section is also important in maximizing the transmission of sound, too thick, less response, too thin, likely to warp or break. It takes years of experience to get it right consistently, which is why a good bridge usually is quite expensive, but well worth it.
You might see advice on the internet that suggests you just go buy a blank bridge and cut it yourself. This is profoundly mistaken. It takes years of training and practice to master the skills to cut a good bridge, and even to recognize a good bridge blank. As the bridge is a vital element in having a responsive instrument, this is not something to compromise on. Do not do this. One look at the articles on bridges linked later in this article and it should quickly become obvious why this is something best left in the hands of an experienced professional.
The variability of carving one sees in bridges is due to differing concepts as to how to best achieve a balance of these elements for a particular instrument, although most luthiers do have a general, recognizable design philosophy. Some people think that the Belgian bridges are better for darker instruments, but I am inclined to think it is more a matter of the physics of the volume of wood more than the blank type. I have seen many white, thick, broad-grained, short-legged bridges made by people who are not well-trained in places that are not near an important luthier, which is why I cringe when I read someone say that they will make a bridge for $90US. If you don’t have good material and you cut corners with sub-optimal (but faster) proportions, you can have a lousy, cheap bridge. If you save your money and see a true artist, you will be glad of the result. This is one of the reasons why a cheap factory-type instrument can sound quite decent or horrible. If you ever have the chance to compare a bunch of blanks, try dropping them from a short distance (on a horizontal plane) onto a hard surface and compare the sound. A dry (darker) tighter-grained blank “rings” more than a soft, white one.
Janos Starker experimented a lot with different bridge designs, as I recall. There was, at one point, a “Starker” blank with an “S” instead of a heart in the middle. He tried bridges where the feet/legs had a conical-shaped hollow at one point. Fast response and not full-spectrum is what I recall of that experiment.
Articles about bridges:
https://www.aitchisoncellos.com/cello-bridge-design/
(download of this link can be slow, scroll down to page 6)
https://stacks.stanford.edu/file/druid:gh900xs0490/CAS_gh900xs0490.pdf
Warped bridges
Bridges warp due to the uncorrected movement of the bridge caused by significant changing of pitch of the instrument, as the friction of the strings pulls it in the direction that you are moving the pitch. You need to ask your luthier how to adjust for this, it is basic maintenance that one can learn to do and must be done periodically, particularly when the weather changes requiring one to significantly retune, or when changing/breaking in new strings. He/she will have to do this when they put a new bridge on, so this is a perfect opportunity for you to learn this important skill. If you do not learn to do this or have it done for you, you will warping bridges forever. This is a basic and important skill that every cellist needs to know and none are taught. I have bridges that I have kept for decades (different heights for different seasons), and none of them has warped.
Straightening a bridge that has pulled forward
https://www.aitchisoncellos.com/cello-bridge-care/
There is lots of very bad advice out there on the internet about how to fix a warped bridge. Principally this involves steam or hot water to soften the bridge. As the best bridge is dense and dry wood, it should be obvious that such treatments are bad for sound, but they also weaken the structure of the wood, making it more vulnerable to further warping. So, if you want to have a bad sounding bridge that warps regularly, follow this advice. If, however, you want to take good care of your instrument, and enjoy its maximum playing potential, visit your luthier and learn to monitor and adjust your bridge. Or have them do it for you. In the event your bridge does warp a bit, they can use dry heat to straighten it if it isn’t too badly deformed.
A mute will not cause the bridge to warp or otherwise damage it. I hate the rubber practice mutes, personally, in my experience they distort the tuning of the cello, which is much worse for your bridge than anything. Never leave the mute on the bridge when you are not using it or when it is in the case, that will cause trouble.
Location of the bridge
The inner hash marks on the F holes should align with the center of the side of the bridge feet, and the feet should be equidistant from the F holes. The side of the bridge closer to the tailpiece should be perpendicular to the top (the side closer to the fingerboard should look like it is leaning slightly back towards the tailpiece when viewed from the side). This is because the back of the bridge is uncut and flat, whereas the front is where the bridge is thinned to the proper shape, wider towards the feet, narrower towards the top. The bass leg of the bridge (that which is under the C string) should be centered over the bassbar, and the feet should be cut and placed so that they are located equidistantly from the F-holes.
Here is a video that demonstrates how to put the bridge in the correct place, and keep it standing up straight:
