Polymetaal

A technical dictionary of printmaking, André Béguin. EN

" Take a plate that has been forged in the way just described and work on the more uniform side, the one that is less straw-like and less chapped. Lay the plate on a slanted board and put two nails or nail tips into the board so as to hold the plate and prevent it from slipping.
When you begin to polish, take a big piece of sandstone and some clean water. Rub the plate firmly with the sandstone once lengthwise all over and once heightwise, making sure that you wet the stone every now and then. When this is done the plate should not have any more hollows left nor should one see the marks left by the smith's hammer blows. The plate should not have any other holes, straw marks, or other inequalities. Then wash the plate down so that it be perfectly clean.
Take some pumice stone, chosen for this purpose, and rub the plate with it using water as you did with the sandstone. Rub it both lengthwise and heightwise, so many times and so firmly and evenly that the plate no longer shows any of the scratches produced by the sandstone. When this is done wash the plate down.
Now repeat the same procedure using a soft whet stone and water until the scratches of the pumice stone have been removed. This kind of whet stone is usually the colour of slate but there are also some that are olive green or red.
Once this step has been accomplished wash the plate well with clean water so that there will be no dust or other dirt on the plate.
You will now need some charcoal that must have been chosen and burnt in the following manner. Saw three or four branches of a very soft willow tree, the branches being fat and full without any cracks; the type that is used by jewellers for sodering.
Remove the bark perfectly well and put the branches into the fire together. Cover the willow with some burning branches and a large quantity of glowing embers so that your pieces of willow do not get much air for an hour or for an hour and a half, depending on their size. Remember that the fire must transform these branches into charcoal all the way through and that no vapour must be left. Because of this it is better to leave the willow branches in the fire too long than not long enough. When you think that they are ready remove them from the fire and put them all into a large container where thay can soak in ordinary water. When you take the willow out of the fire throw it into the water when it still red hot in order to put the embers out and cool the pieces ioff. Some people use urine for this step but as far as l am concerned water will do just as well.
Now, in order to finish polishing the plate with these pieces of charcoal you must choose a whole branch or a piece of a branch that is both big and strong and which has also withstood the fire well in that it has not cracked all over.
Hold this piece of willow charcoal in your hand and press it onto the plate so that one edge rubs the plate. Rub the plate until the signs left by the whet stone have disappeared. This time it is not necessary to follow any particular direction. lf the charcoal only slips on the plate surface without catching somewhat it is no good and another piece must be used which will catch when you rub it on the plate surface with some water. The rubbing should produce a soft noise and, when you hear this noise, you may procede to rub back and forth in the same direction as long as it takes to remove all the scratches, holes, and bumps on the plate, no matter how small they may be.
If by any chance (as it happens quite often), the charcoal is too hard and rough and therefore cuts too deeply into the copper plate you will have to choose a somewhat softer one with which to polish the plate again.
Once you have done all you can with the charcoal and the plate has an even finish without any deep scratches or holes it is time to use a well polished steel tool that is either rounded or flatened so as to have a point shaped like a heart. This tool is called a burnisher. First rub the plate with a bit of olive oil and then rub the burnisher over the surface pressing down firmly. The best way to burnish a copper plate is to rub the burnisher diagonally (i.e. from one corner towards the opposite one) rather than horizontally or vertically. By burnishing this way it will be easier to remove the scratches and soiling made with the charcoal. The copper plate must be burnished all over its surface until it shines like a mirror. lf by any chance there should still be some scratches these and only these should be removed with the burnisher. Use the burnisher on these scratches in lozenge-shaped movement until nothing is left.
Once the plate has been properly polished and burnished it must be washed down with clean water and dried exposing it to the fire with the reverse side pointing towards the flames. The heat of the fire will dry the water drops left on the worked side of the plate. When the plate is dry it should be wiped with a clean cloth. ln order to be sure that there is no grease left on the plate you may rub it with some well kneaded bread crumbs or then dust it with some very soft chalk white (talc) which can be rubbed on the plate with a white cloth. Then the plate must be wiped so that no bread crumbs, chalk, or extraneous matter remains.
When the plate has gotten to this point it is ready to receive the resin ground. One can also make sure that the plate is perfectly polished by sending it to the printer who will ink it all over as if it were already engraved. He will then pull a proof on white paper and, if the copper plate is perfectly polished, the sheet of paper should maintain its perfect whiteness. lf the plate is printed this way it will be necessary to remove all traces of grease and all of the black ink or otherextraneous matter."

At present the polishing of plates is done either by hand or using a machine. The machine, of course, does the lob much faster but nevertheless the polishing must be done carefully because if the plate is incorrectly held, heated up excessively, or irregularly polished the result may be that the surface is "chanelled", bumpy, or bent even though perfectly shiny. Quite a bit of practice is needed in order to hold the plate correctly against the mills, the brushes, etc. so that the result is perfect. The pumicing is done first (with increasingly fine abrasives ), followed by the polishing (metal brushes, silk brushes, felt or heavy cloth brushes, all of which are used with wet emery powder, powdered red, oleine, oil, etc.). lf a polishing machine is used remember to place the plate on a supporting surface. Present it to the brushes or the revolving strip, whatever the case may be, in such a way that you can hold the plate with your knee. The work should be done sitting down so that the plate can be moved back and forth in a regular right to left movement. Both sides of the plate should be polished.
Hand polishing can also be done using powdered pumice stone and willow charcoal that has been well oiled or thoroughly wetted with water or mineral oil. The charcoal must be rubbed in such a way that it will wear down diagonally. Sometimes abrasives are used which have a varied grain [* abrasives].
The job can be begun with a dry pumicing using medium sized abrasives such as 100 or 120 grade. Then, slowly, move to sizes 400 and 600. The pumicing is finished off either under a thin trickle of water (on zinc plates) or with oil (on copper plates). The polishing itself is done with a clean rag or a polishing machine and some product that will make the plate shine.
ln polishing a plate do not push hard on the abrasive or drag it to the end of the plate. Remember that it is not necessary to polish a plate to a high finish. At times a well done mat finish will produce a good white and will be more resistant. [* abrasives, burnishing, scouring, planing, pumicing].

[2] Polishing a lithographic stone. lt is necessary to polish a lithographic stone when one wishes to make a very precise pen drawing or when one wants to engrave the stone. This kind of polishing can be done by rubbing with a pumice stone brick or by using an acid. "lf one removes the acid from a stone by wiping it and one then rubs the surface with a wool cloth, once dry, the stone will take on a polish that is lust like a mirror." (Senefelder).

[3] Polishing a bumisher. A burnisher must always be very well polished otherwise it may scratch the very surface it is meant to polish. Polishing should be done on a soft wood board " in which two hollows have been made, one of which containing emery dust and the other English red and oil". The products necessary for polishing a burnisher can be found at any ieweller/watchmaker supplier.