Printing ink  [1] [ Encre noir ]. This [ink] used for printing books is a mixture of oil and black [pigment]; the oil is converted to a varnish by heating and the black comes from resin. All the particles that arise from this sort of resin are collected by a clever method when it is burnt in a specially-designed building called in the trade a sac à noir which will be described later in this article.

The vessel to be used to make the varnish can be iron, cast iron or copper; the copper ones are usually made in the shape of a pear , and are named from this, the others are the shape of ordinary cauldrons. Whatever the material of the vessel and whatever its shape, it must have a copper lid with which it can be very firmly closed at will. The vessel must be fitted with two iron rings approximately in the middle a little higher than the lid which has its own ring. One or two poles can be passed through these rings by which it can be carried safely between a man on each side when it is to be removed from the fire or replaced on it.

For safety it is prudent when making the varnish to choose a wide space such as a garden and not to be near a building.

If one wishes to have, as I shall assume, one hundred pounds of varnish after reduction, put in your pear or cauldron one hundred and ten to one hundred and twenty pounds of walnut oil; note that this amount, or whatever quantity is to be used, must not fill the vessel more than two thirds at the most to give enough space for the oil whose level rises as it heats.

Now, close the vessel with its contents very firmly and put it over a clear fire where it will remain for two hours. If the oil catches fire during this first heating, as will happen, take the vessel from the fire and cover the lid with several pieces of wet old linen or cloth. Let the oil heat for some time at such a temperature that it does not catch fire spontaneously but [lights] only from time to time [intentionally] and with care. When the fire dies down uncover the cauldron carefully and stir your oil well with an iron spoon; this stirring cannot be repeated too frequently as it is on it that good preparation very largely depends. When this is done, replace the vessel on a less hot fire and, as soon as the oil is hot, throw into it a pound of bread crusts and a dozen onions, which speed up the degreasing of the oil, then cover the vessel again and let it boil over a very low fire for about three hours on end; during this time your oil will be perfectly cooked. To know [when this stage is reached] and to reassure yourself about its state, you dip your iron ladle in the oil and drip the oil that sticks to it on a slate or tile; if this oil is sticky when cool, and spreads somewhat like thin glue, this shows that it is ready and from then its name changes from oil to varnish .

The varnish thus prepared must be transferred before it cools into vessels in which it will be stored; it must be passed several times through a piece of good linen or a specially-made filter  [2] so that it will be so clean that it is perfectly clear.

Two kinds of varnish are needed; one thin [3] for use in cold weather and the other thick [4] for hot weather. These two varieties are also essential since one must often modify one [by mixing it] with the other.

Thin varnish can be made on the same fire as the thick but in a separate vessel. But one can also use linseed oil for this varnish, and I prefer this because it becomes less brown and less dark on heating than does walnut oil and this makes it more suitable for the red ink which we shall describe.

For its quality, thin varnish demands the same care and precautions as the heavier varnish; the entire difference is made by using only a moderate degree of heat, but managed in such a way that, while sharing the good qualities of thick varnish, it is less cooked, thinner and less sticky than the thick.

If one wishes to make this lighter varnish from the same oil as used for the thick variety, and this is only a small inconvenience when it is to be used for red ink, or to save oneself the work of making it separately and from different oil, it is very easy to take advantage of the first heating of the latter and, when one sees the required properties have been achieved, to draw off the desired amount from that which is on the fire.

Linseed and walnut oils are the only ones suitable for good printing varnish and walnut oil is preferable in every way; as for other kinds [of oil] they are worthless because they cannot be completely degreased and they stain the impression as it is being printed or turn it yellow as it ages.

However, some printers use rapeseed oil or hempseed oil but this is to print books for the bibliothèque bleue  [5]; this use is of little consequence for one can be sure that it is done intentionally for poor [quality] work.

There are some printers who believe it necessary to add turpentine to the oil to make it thicker and quicker-drying. It does have these effects but also produces disadvantages. The first is the difficulty of cooking it so precisely that it does not make the varnish too thick, which is rarely avoided; the varnish is so thick and heavy that it rests on the surface of the paper on the forme and saturates it very quickly; if the turpentine is fully cooked it forms a liquid paste containing little hard grains like sand which do not ever grind down.

Turpentine, like litharge which some people use, and make a great secret of, also has the fault of attaching so firmly to the type face that it is almost impossible to wash the formes satisfactorily however hot the lye is; also, these [materials] dry and harden so fast that, as well as making difficult the distribution of the type so firmly are the letters stuck together, they also fill up the type face to the point where there is no hope of cleaning it and thus put type that has seen little use into the deplorable condition of having to be melted down.

If, by negligence, one were to use very newly-pressed oil to make varnish, turpentine would have to be used because the impression would inevitably be stained; in these circumstances one can add a tenth part [of the volume of oil] that is cooked separately for the same time, in the same conditions and with the same precautions as the varnish. It is boiled for about two hours; to find out if it is ready one soaks a piece of paper in it and, if it crumbles to powder with nothing left attached to the paper on rubbing it as soon as it is dry, the turpentine is cooked sufficiently. With your varnish taken off the fire you pour this turpentine into the same vessel, stirring vigorously with the iron ladle, then put it all back on the fire for half an hour at most, stirring all the time so that the varnish combines with the turpentine. The way to avoid the use of turpentine and litharge and the problems they cause is to use only very old oil [to make the varnish].

Le sac à noir  [6] This consists of four little pillars three or four inches square and seven or eight feet high held together by two crosspieces; all its dimensions are at the whim of its builder. The top is a well fitting, solid ceiling; the base or ground level must be paved or tiled for safety. A low door is provided to enter and leave this little chamber and all the walls are made of good cloth, new and stretched out as tightly as possible, held by [rows of] nails two inches apart. When this is complete you glue very strong paper all over the cloth  [7] and take care to stop up any visible openings so that the smoke cannot leak out anywhere. A sac à noir lined in this way is adequate but it will last longer and is more leak proof if it is lined with well-clipped sheepskins.

It is in this sac that the resinous material  [8] is burnt to produce smoke black. For this, a quantity of resin is prepared by boiling and melting in however many pots are needed for the amount. Pieces of rolled-up paper or wicks coated with sulphur are pushed in, then the pots are placed in the middle of the sac , the wicks lit and the little door shut very firmly on leaving.

When the resin is consumed the smoke will be deposited over all the interior of the sac à noir and, when this has cooled, you go in and cover the pots and close the door again; then, beating the outside all over with sticks, you make the smoke black fall off [the walls] and collect it into earthenware vessels or the like. Since brushing up the black with a broom may mix dirt into it, you take the precaution of putting some water in the bottom of the pots so that, when they have settled, you can skim off your black (or collect this in some other way) to put into a suitable vessel and keep. This smoke black is without doubt the best material one can use for printing ink; two and a half ounces are used for each pound of varnish - I assume a pound of sixteen ounces; however, the [actual] amount of black to be used must be decided by eye according to the colour of the ink.

All that is needed to combine the smoke black with the varnish is to mix them together thoroughly; to mix them several times stirring very well each time so that the whole forms a thick soup that leaves many trails when it is separated into lots.

In some print shops the smoke black is mixed with the varnish only on the ink block with the quantities again determined by eye. The only disadvantages I see with this way of making the ink are the risk that it is not rubbed out enough, because this takes some time, and that ink made in this way by different workmen is not all of the same colour throughout the print shop. From this I deduce that it is better for all the ink to be prepared together without relying too much on the pressmen.

Red ink: This ink is used quite frequently and is practically indispensible to the printing of breviaries, books of offices and other books for the church, sometimes it is also used for book advertisements and for decoration of first [title] pages.

For red ink , medium varnish is the best; it must be made from new linseed oil in good condition because this does not darken on cooking as does walnut oil and because the varnish must be as clear as possible. The smoke black is replaced by cinnabar or vermilion well dried and ground as fine as possible. In an ink vessel [on an ink block?]  [9] reserved for this sole use you put a small amount of varnish on which you throw a little vermillion then mix and grind it all with the brayer  [10] then you pick up with the slice  [11] of the ink block this first amount of ink from the bottom of the vessel and repeat this process several times until you have used, say, a pound of varnish and half a pound of vermillion. Some people mix into this first compound three or four ordinary spoonfuls of wine spirit or brandy in which has been dissolved forty-eight hours earlier a little piece of fish glue the size of a nut. I have found from experience that this mixture does not fulfil all the functions attributed to it; it is more reliable to add to the given quantity of red ink five sixteenths  [12] of an ounce of the best carmine which improves the colour of the vermillion which is often not as good as one might wish; it adds to its brilliance and prevents it from becoming dull. This is more costly, I admit, but more satisfactory. When, then, you have added these materials you begin again rubbing out your ink so that it will be neither too thick nor too thin; red ink is very prone to clog up the face of the type. If, as happens, you do not use all the red ink you have made, to keep it pick up your ink block by the edge and fill it with water which you keep replenished so that the vermillion does not become dry and form little pellets on the surface of the varnish, from which it separates due to the effect of a hot dry atmosphere.

Although only the two kinds of ink that we have just described are in common use, other colours can probably be made by substituting for the smoke black or vermillion the necessary pigments to produce different colours. One could, for example, make green ink using calcined and prepared verdigris, and blue ink with Prussian blue prepared in the same way; or yellow with orpiment; or violet using fine lacquer calcined and prepared, by grinding these pigments thoroughly with varnish similar to that of our red ink . The preparation of the verdigris, Prussian blue and fine lacquer consists in mixing with them lead white to lighten them; without this these pigments would produce too dark an ink .

1. Unusually for the articles on printing in the Encyclopédie , much - though not all - of this article is in the second person. I have tried to preserve this style in the English translation.

2. chausse Presumably the filter was shaped like a stocking.

3. foible

4. fort

5. bibliothèque bleue Popular works intended for the masses and issued in blue covers, they were poorly printed.

6. This sort of tent for making smoke black is a less sophisticated device than that described as being used in Germany for the same purpose in the article Noir de fumée .

7. Presumably the paper is glued to the outside of the tent, though the text does not make this explicit.

8. Poix résine Resin obtained from resinous trees.

9. As it is written the text seems to imply that the red ink is made on an ink block reserved for this purpose. However, two points suggest that this was perhaps not so for the whole process; first, Le Breton says: Vous mettez dans un encrier reservé.. and not sur un encrier .. as is usual in speaking of the ink block (which is a sort of open tray). Secondly, he speaks of a pound of varnish and half a pound of vermillion which seem large quantities to work on the ink block rather than in some kind of mortar. On the other hand, later he clearly does mean the ink block when he talks of picking up the encrier par le bord . So perhaps the red ink really was made entirely on the ink block?

10. le broyon A wooden pestle called by Moxon the brayer .

11. la palette A palette knife called, once again by Moxon, the slice .

12. un gros et demi A gros was a drachm or one sixteenth of an ounce.