Most harmonicas nowadays are pretty good out-of-the-box. At least if you choose to pay a little bit over the bare minimum. Still, as people get more and more sophisticated in their playing some choose to get a custom or semi-custom built harmonica. This is a harmonica modified or built by a skilled craftsman. I have harmonicas built by Günther Bayer (semi-custom), Dick Sjöberg (custom) and Joel Andersson (custom). I am very pleased with those harmonicas. In this article I will touch upon a modification you can do yourself with very little work. That is, changing to a custom harmonica comb.
I first came in contact with custom combs when when my first harmonica mentor Dick Sjöberg was developing the Sjoeberg Comb some years ago. It was part of my first custom harmonica that Dick built for me. Nowadays the Sjoeberg Combs are manufactured by Joel Andersson of J.A. Harmonicas. If you make a Google search you can find other suppliers of combs.
Changing the comb on your harmonica to a custom harmonica comb is a good way of optimizing an existing harmonica and put it closer to the performance of a custom harmonica. What you will normally get is less leackage and more focused air stream towards the reeds. This will result in a harmonica that require less effort to play and bends will become easier.
The first thing you need to consider is if the custom harmonica comb will fit yout harmonica. Normally the manufaucturer will be very clear about this but it doesn’t hurt to be extra sure. I once got a comb I thought would fit a Marine Band deLux that was actually for a Marine Band Classic. Fortunately I could return it.
Properties of a custom harmonica comb
A custom harmonica comb is very often made out of hardwood and is fully sealed. This means that it will not absorb moisture and will keep its shape much longer. The surfaces that meets the reed plates are extremely flat to ensure a tight fit. The slots in the comb may also have a different design than you are used to. This is to control the air flow going to the reed. Some custom combs also include details like brass tube resonators to add to the overtone properties of the harmonica.
Preparing the harmonica
To benefit from the flat surface of the comb the surface of the reed plate needs to be as flat as possible. The reed plate for the blow notes has the reeds attached towrds the comb so unless you plan to remove all reeds first there is not much you can do about that plate.
What you should do is to make sure that the surface of the draw reed plate that faces the comb is as flat as possible. If you run your finger over an untreated reed plate you will feel that the pins that are used to attached the reeds stick out just a little bit. If they are left like that you will get some distance between the comb and the reed plate. This is especially true if the comb is made of hardwood. Tightening the screws will not help, the reed plate will most likely become a bit deformed.
Getting a good result
To make the reed plate as flat as possible you sand it starting with sand paper around 240 and then changing to finer and finer grade. For the final stages I use lapping paper which has extremely fine grains. This will create an almost mirror like surface. I hold the reed plate down using three fingers and move it in a figure eigth pattern to minimize the risk of an uneven surface. Also make sure that there are no unsanded spots left when you are done.
You need to make sure that the surface you lay the san paper and lapping paper on is as flat as possible. A table top may suffice, just realize that it is not 100% flat. I have gotten a piece of hardened glass that is pretty damn close to flat. The professionals use a lapping plate which is extremely flat to get the best result possible.
Putting it all back together
Once you are happy with the surface of your reed plate you can install your new custom harmonica comb. Reassmble as you normally would but don’t tighten the screws too much, there is no need for this. If you tighten too much you run the risk of deforming the reed plates.
If you don’t have a custom comb you can actually get some of the benfits by flattening the standard wooden comb the same way as the draw reed plate and reassmbling with some non-toxic mineral oil between the reed plates and the wooden comb. This will give tighter seal and prevent the standard comb from absorbing moisture.