The Thin End of the Wedge: The String player's bow on the luthier's bench

From time to time every bow needs some maintenance. It has surprised me to see how much wear and tear bows and instruments suffer, but thankfully there is much that can be done to reverse the process. When a player brings in a bow and says it needs a rehair, it it usually well over due and other maintenance is often required as well. The level of skill and attention to detail required is often not understood or appreciated. In this post, I am offering a window into my world and hope you will learn something interesting about this fascinating art of bow restoration.

The bow which is being rehaired here is a viola bow of reasonable quality, with a silver ferrule, whalebone lapping and good quality leather grip.

(at the bottom of the post there is a glossary of terms used)

preparation

After first examining the bow for any damage, potential problems or idiosyncrasies, the first task of the luthier is to carefully take the bow apart. This is not always easy, depending on how the bow was made or how it was previously rehaired. The only part of the process that should involve glue is the insertion of the spreader wedge into the ferrule. Sometimes other parts of the bow have been glued together which makes the job of taking them apart time consuming and risks damaging the bow. The art of a luthier includes respect for their colleagues who may have to take part the work again at a later date, and respect for the integrity and longevity of the bow itself.

If the ferrule or slide are tightly fitting, then there are ways to remove them. The ferrule can be placed in a small vice, flanked with cork to protect it, and the frog gently prised off with a side to side movement. The slide can be removed using a rubber band or double sided tape.

This particular viola bow came apart easily as it had been well made and well maintained. A prayer of grateful thanks was offered up to the previous luthier who’s bench it happened to come across.

cleaning

Before replacing the hair in the bow, the parts of the bow need to be cleaned with appropriate materials.

For the stick of the bow, I use my homemade violin polish. It is non abrasive but effective and has a lovely smell, due to its secret ingredient....if a bow stick is thoroughly coated in old rosin then a more abrasive cleaner and a different method are needed.

I clean the thumb leather using a leather cleanser from RaceGlaze.

If the lapping is made from silver then a small dab of silver polish can be applied to clean it bearing in mind the gaps between the lapping and ensuring not to get the liquid between these.

the thin end of the wedge

After cleaning, the wedges are prepared for the rehair. 

All the wedges are trapezoids of various sizes and can be cut using the same method. This is difficult to get the hang of and takes a lot of practice. I started by measuring the depth of the mortise with a stick or caliper but now I’m more experienced I can just assess this by eye. It is essential to use a sharp chisel and cut with the grain for the facing side of the wedge which will face the tip for the tip wedge and the screw for the frog wedge. The wedges need to be almost an exact fit, but not quite as they need to allow room for the hair at the top end (tip) and the bottom end (frog) of the mortise and their mustn’t be too much pressure on the sides of the mortise at the tip end as this can break the stick, so tiny gaps need to be left on either side of the mortise. 

The wedge for the tip and the frog are made of maple wood and the wedge for the ferrule is made of willow or poplar. 

The photo to the left demonstrates what the piece of wood looks like before I start cutting and on the right the photo shows me checking the wedge for fit as I go along, removing little by little until the final shape is reached. I like to start at the tip end, but some luthiers start at the frog end.

the frog and the spreader

This sounds like a name of a quirky pub, but these are more wedges, cut in the same way as the tip wedge but to very different dimensions. The frog wedge is the easiest to cut, to my mind, and the spreader wedge is the hardest. This is because it needs a few very minor extra slithers with the chisel in exactly the right place to ensure the hair spreads properly. Also, because the mortise is so slender, the height of the wedge is small and also tapers toward the inside, which is difficult to get right.

the hairy bit

Hairy in more ways than one, this part of the process is the do or die part. Selecting the hair is no big deal, as long as you get the right amount for the right bow, be it violin, viola or cello. Tying the first knot is okay too. The key is to get the string under tension and master a slick process of winding it around the hair catching the end underneath as you go. Tying it super tight is essential. Sometimes it’s not tight enough and you have to do it again but at this stage this is ok because you haven’t cut the hair to length yet. Tying the knot at the other end is the hair raising bit....

But before that, the knot must be secured by burning off the ends dipped in rosin, as shown in the first and second photos on the left....this is really fun for me, as a non smoker with no other occasion in life when I need to use a lighter.

When the hair is inserted into the tip you find out whether your wedge is really as good a fit as you thought. Sometimes it needs some adjustment to fit the hair in. You can see from the third the left what the tip will look like when you’ve got both the knotted hair and the wedge in.

Now that one end is secure, the rest of the hair needs to be given a good soaking, so out comes my shallow pie dish, hair gets dunked in, and I’m off to dunk some biscuits in a cuppa while I wait....

the HAIRDRESSING bit

Combing out the hair reminds me of Sunday evenings sitting by the fire when my Mum used to run a comb through my wet hair. An impatient or rough technique is not appropriate here as the hair is fragile and all knots must be removed, starting at the cut end and working upwards. I start with a wide tooth comb and then switch to a fine tooth comb such as a nit comb, when the biggest tangles have been removed. The hair needs to stay wet throughout so if it takes too long, it just needs to be dunked back in for a moment,

When the hair is completely knot free, I run the comb through it a final time, taking care to line it up with the mortise in the frog end of the stick, and pulling it gently to judge the length. The hair is pinched together with one hand while the other hand takes the string in preparation for the second and fateful knot. If this one gets tied too short then the hair is doomed and The Hairy Bit needs to be started again.

A small but important action is needed after tying the knot but before inserting this end of the hair into the mortise, and this is something that to start with I used to continually forget to do, in my anticipation of finishing what was at first an agonisingly difficult process. Slipping the ferrule into the hair....it simply cannot be done at any other point and if it only dawns on you that you haven’t done it once you’ve put the frog wedge in. You just have to take that out again, which can cause enough damage to the wedge to mean a recut. It also needs to be put on the right way round. The edge of the ferrule closest to the frog can be sharp, and would end up cutting the hair when the spreader wedge is inserted. The end of the ferrule which faces the tip of the bow should have a chamfered and filed edge. As well as forgetting to put the ferrule on entirely I have also put it on the wrong way round before and then cut the hair with the sharp edge while inserting the spreader, a most disheartening turn of events which involves starting again from the beginning of The Hairy Bit.

I’ve now created a checklist for the whole rehair process to prevent unforced errors like these ones.

Needless to say extra time is taken to assess and judge where the knot needs to be tied. The hair needs to be neither too short nor too long. Just right is when the hair can be tightened the right amount for playing and loosened the right amount to relieve the pressure on the stick for storage. I’m relieved when this part if successfully over, but the proof is in the pudding and in this case the pudding is not served until the spreader wedge is in, which is the next stage....

the happy medium

The moment of truth comes ever closer now, as the knot is inserted into the frog mortise, followed by the wedge, and then the slider is carefully eased back into place, before slipping the ferrule down the length of the hair and onto the end of the frog,

It’s time for the slightly messy bit, with the application of just the right amount of glue onto the spreader wedge; another step in this journey which requires a careful judgment between one excess and another - the happy medium. Glue is not my happy medium. I am much happier with a knife or chisel than with any sticky substances, however, I am learning to be a bit more dexterous and not get glue all over myself or my bench, I use Titebond for this bit, as it has the right strength required without taking too long or too short a time to dry. Superglue is frowned upon. It is too strong, too difficult to manage and impossible to remove if you misplace it. It also dries too quickly.

I insert the spreader wedge into the gap inside the ferrule and push the free end of the wedge against the bench to push it as far in as it will naturally go. If it sticks out a little, then the excess can be very carefully cut away with a round ended chisel, but It is best to cut the wedge to exactly the right size before inserting it as any cuts that are made once it is in place are very risky. It would be too easy to slip and cut the hair.

Once the spreader wedge is in place a bit of patience is needed before inserting the screw and tightening up the bow to see if the length is correct. The glue needs to dry and the hair needs to be completely dry. Because of all the natural breaaks in the rehair process, other jobs can be dipped in and out of or even two rehairs tackled at once (this is a bit too much pain for me in one day!).

Alternatively, having daughters that need picking up or dropping off places is another way to pass the time while waiting to see if your work was in vain or not...

On this occasion, I am happy to report that this viola, with a new lease of life, is now ready to be played with again.

If you've got to the end of this post, then well-done and thanks for reading about my rehair journey.