The sinking is the first part of the panmaking. During the sinking the panmaker lowers the bottom of the drum into a concave kettle where the notes later are hammered up as convex dents. The whole sinking process can be seen as consisting of four steps marking, lowering, shaping, and smoothing.
There are several reasons for doing the sinking: First, the bottom is lowered to remove the tone of the bottom of the drum - otherwise it would interfere with the sound of the notes. As the bottom is sunk you can hear its tone rise from a low pitch up to a very high. Second, the bottom is stretched to enlarge the surface to make enough space for all the notes. Third, the metal is made thinner in the middle where the highest notes will be situated. Fourth, the sinking is intended to make a suitable overall curvature for the notes of the different pan types. There seems to be a certain (still unrevealed) relationship between the size of the notes and the needed overall curvature of the pan - small notes deeper sinking - large notes a more shallow sinking.
If the bottom rim has some indentions you have to start by making sure that the rim is circular. This is done by hitting the rim with a sledge-hammer from the middle of the bottom surface and outwards. If the side of the drum has some large indentions it is best to open the drum in the top and remove the dents by hammering from the inside. Otherwise they might affect the sound of the outer notes.
Begin the sinking process by opening the drum to make it possible for the air to come out when you are hitting the bottom. This can be done either by removing the whole top or the plug, see fig. 2.1. Then turn the drum upside down and place it steadily on the ground. A few strokes on the top before turning the drum may make the top concave and help the drum stand better.
Fig. 2.1 Remove the plug to let the air slip out during the sinking.
The panmaker often starts by drawing a pair of concentrical circles on the bottom surface to make it easier to see the shape of it while it is lowered. To draw the circles, the middle of the bottom has to be found and marked. This is usually done by making four pencil marks on the bottom at equal distance d from the rim. Draw straight lines through the marks and then two lines between the opposite corners of the formed rectangle, see fig. 2.2. The crossing of the two later lines represents the centre of the drum. Another method to find the centre is to measure the distance 26.6 cm, which equals the radius (half the diameter) of the drum, from the rim towards the centre several times at different rim positions.
Fig. 2.2 Method to find and mark centre.
Two concentrical circles are made by using a compass. The inner circle is drawn with a radius of approx. 1/3 (10 cm) of the drum radius and the second with a radius about 2/3 (20 cm) of the whole radius. The result is that the drum radius is divided into three equal parts, see fig. 2.3. The two circles may also be drawn by moving a ruler round the bottom of the drum in circular movements, drawing two lines at constant distances from the rim, see fig. 2.4
Fig. 2.3 Concentrical circles drawn to see the shape of the bottom better while doing the sinking.
Fig. 2.4 Method to make concentrical circles.
The lowering of the drum bottom is done using a sledge-hammer with a smooth, rounded head and a short, specially formed handle. The handle of the sledge-hammer should be long enough to enable you to hold it with both hands.
A better, more elaborate method to do the sinking is to use a 5 kg cast iron ball, most often a shot-put or a cannon-ball. The ball is dropped or thrown at the bottom and caught when it bounces up again. The round ball will make fewer marks in the metal than the sledge-hammer, but it will be harder to work on the steep sides near the rim. For the inexperienced panmaker the shot-put may also cause difficulties in hitting the right spot and catching it when it bounces back.
Fig. 2.5 Sinking with a shot-put. Photograph by Linus Torell.
It is important that the surface of the sledge-hammer or the ball is very smooth, otherwise it will create impressions that later will cause small cracks in the stretched metal. For more detailed information on the sinking sledge-hammer and the shot-put, see appendix B.
The first strokes should be placed near the outer circle. Work around the drum along that circle. If the head of the sledge-hammer is well rounded and you keep it perpendicular to the surface when you hit, you may use all your strength at this point. Using a shot-put, its weight alone will supply enough force, you just have to lift it and let it fall.
After the first circular work-around you start to place the strokes closer to the centre, thus working towards the middle in a spiral-like manner, see fig. 2.6.
Fig. 2.6 Sinking method.
During the sinking, the drum should be standing on a flat, semi-soft surface, like a carpet or directly on the ground if you are outdoors. This will make it easier to keep the drum in a fixed position while you are hitting. It might also be beneficial to have someone to hold the drum to prevent it from jumping around.
When you are working near the edge it is usually better to use one hand for hitting and the other one to support the drum. But keep the thumb of the supporting hand on the outside to prevent yourself from hitting it with the ball or the sledge-hammer. Best is to place the supporting hand a bit away from the hitting point. Protective gloves (and something to shield your ears from the noise) are also recommended.
After the first spiral movement towards the centre you start again, this time further out, a bit closer to the rim. Now work the metal by, so to speak, "driving it from the rim". This means that you first hit the surface hard near the rim, then move towards the centre, hitting a bit softer each time, see fig. 2.7. This working pattern is repeated time after time, while moving slowly round the drum.
Fig. 2.7 Working from rim towards centre.
It is more important to have a good feeling for how the surface is shaping, than it is to work systematically. There should not be any large fluctuations anywhere - if an "edge" is coming up in the metal, lower it right away. Keep your eye on the concentrical circles - the best way to control the sinking is to move slowly backwards while you are working. In this way you can see the formerly sunk surface to keep the newly sunk levelled with it. It is also beneficial to rotate the drum now and then to prevent the light and the shade from fooling you to make a non-symmetric sink.
To be able to shape an evenly curved sink, it is important to keep the middle part level (like the bottom of a bowl) with the rest of the surface. Do not hit too much in the middle, though, because the metal will easily get too stretched there. A couple of strokes when it is beginning to come up as a dent and starts to emit a resonant sound (like the one from a big note) is usually enough do keep it down.
Keep working around the drum according to the above pattern, inwards from the rim, thus shaping the surface to a smooth bowl. Most of the effort in sinking should be concentrated to the region between 1/3 and 2/3 of the radius of the drum. This is where the inner end of the outer notes will be later on, see fig. 2.8 for an overview.
Fig. 2.8 Region where most of the effort in sinking should be concentrated.
After the sinking the basin in the bottom should have a straight or slightly convex part near the rim. This part is later going to form the outer note dents. Its shape and height should be different for different pans - longer and more convex the larger the notes are going to be. It is important that the shape of this part is right, otherwise the notes will not rise properly when the backing is done. As a rule of thumb, the shape of the basin should be almost as if it was a pan with a continuous ring of outer notes, without any groove indentions between them. This means that the height of the deviation from the spherical should be about the same as the height of the future note dents.
If you are a beginner in pan making you will probably have to read the sections about backing, grooving, levelling and tuning to understand the intent of this shaping. In fig. 2.9, a cross-section of a sunk drum is shown. Moulds for the overall shape of the different pans and their sinking depths are given in appendix A.
Fig. 2.9 Cross-section of drum after sinking.
Note the deviation from spherical concave shape near to the rim.
When you are beginning to reach the final depth you should check the depth at even intervals, see fig. 2.10.
Fig. 2.10 Measure the depth at even intervals.
A fast (and somewhat risky) method to do the last sinking is to lower the drum to the appropriate depth in the centre and then "follow it up" on the rest of the surface, see fig. 2.11 for an explanation.
Fig. 2.11 A trick for the last sinking. Hit down the surface in the middle to the right depth and follow this up towards the rim. Not recommended for beginners.
Handling of holes
If the surface bursts during the sinking you have to decide how to handle the situation. The holes can be divided into two main types small unevenly shaped holes and longer cracks.
The first type of hole is caused by defects such as rust or harder parts of the metal where the carbon content is higher. These holes are usually no problem if they are not close enough to grow into a big crack. Try later to position the notes between them. If that is not possible, consider the possibility to weld the holes before continuing. If there are more than five holes you have probably chosen a bad drum. The best thing might be to discard the drum and start on a new one. I have, though, seen working (but not good-looking) pans with small holes in the note areas, so it might still be worth a try.
The second type of hole, the cracks, is either caused by text grooved in the metal or by too much stretching of the metal in certain regions, or a combination of these. They will show up as small slits and grow as you sink and stretch the surface further. If they show up before you have reached 70-80% of the final sinking depth there is a risk that they may grow up to a length of 5 cm or more, making the drum unusable. The cause of the crack can be one of several the drum is bad, the sledge-hammer is not smooth, or you are doing the sinking in an incorrect way. Your best choice might be to stop here and start on a new drum.
If there are no more than two or three cracks in the middle, try to place the inner notes between them. At a later stage, welding of the cracks might be considered. If a crack is starting to grow you might decide to stop the sinking at a depth 2-3 cm less than the recommended, and place the notes closer to each other. This might be preferred rather than spoiling the whole drum.
Welding can be done either with gas or by electrical methods. The weld should be made as neat as possible and a smoothing of it may be necessary before continuing. Welds in the drum surface should preferably be placed between notes or inside note sections, but not on a groove, because of the risk of cracking when the grooving is done later. Presumably, there are also acoustical implications of disturbing the isolating effect of the groove. Welds in the note area of small notes can be quite disastrous for the sound, but in larger notes they do not seem to influence the sound particularly.
The shaping is the part of the sinking in which the drum basin is adjusted to its final shape. When you reach 90% of the final depth it is time to change tool to the backing sledge hammer, which is roughly the same as the sinking sledge hammer, see fig. 2.12. It has a shorter handle and is held in one hand for more control, see the specification in appendix B.
Fig. 2.12 Shaping the sunk surface with the backing hammer.
Now the marked circles are probably gone together with most of the paint in the middle of the bottom. If so, mark the centre in the same way as before and re-draw the two concentrical circles before continuing with the next step.
Now you start hitting softly, thereby adjusting the shape and smoothing the rather uneven surface at the same time. The only direction the surface can be adjusted is downwards, so it will keep on sinking while you are shaping. Measure the depth at even intervals.
If the surface on one side of the basin is coming up while you are hitting on the opposite side, you are either hitting too hard, or the metal is too thin. Try hitting more softly. If this doesn't help, there is a risk that you eventually will have to discard the drum.
The best method for doing the shaping is still by working the metal "towards the centre", i.e., first hitting near the rim and then going inwards in the same way as described for sinking. When 100% of sinking depth is reached the surface should be smooth and evenly shaped.
It is important that the surface of the drum is smooth. Any unevenness in the metal will affect the overtones and make the tuning harder. If the surface still is rough when the shaping is finished, this is the best time to even out the part of the surface that later will become the note areas. During the rest of the crafting they will be left as unaffected as possible, until it is time for the tuning.
The smoothing is done by hitting down the surface in places where it is dented upwards. The tool used for smoothing is usually the backing hammer, see fig. 2.13. Use good light to see the reflections in the metal working outdoors is the best. Avoid hitting the surface in places where it is dented inwards, work around them instead. As the metal is thicker near the rim you will notice that you have to hit much harder to remove the roughness there.
Fig. 2.13 Smoothing the sink with the backing hammer.
While you are examining the surface for unevennesses, try to locate spots of potential trouble. Examples of such are sharp indentions caused by remainders from welding or lumps in the painting and corrosion (rust) that seems to be going deep into the metal. Mark those places and try to avoid them when you are positioning the notes later. The most hazardous thing to do is to make a groove across such a spot. The weak metal could easily burst when it is hit with the sharp metal punch.
A skilled panmaker often omits this extra smoothing step because he has smoothed the surface enough during the shaping. If there is any roughness left, he smooths the surface later with the backing hammer at the same time as he is doing the backing.