(2) Any great pressure will remove this preparation and the whole paper will take color.
(3) The oil color must be very thin and fluid, because a tougher one will take hold of the fibres of the paper and tear them off.
The foregoing experiences applied to the theory of the print itself lead to the following conclusions:—
(a) The paper to be used for printing must never be too wet, because the most powerful pressure could not remove the water sufficiently.
(b) Paper that is too wet is prone to adhere to the stone with its printed parts, which are likely then to tear away easily, thus damaging or ruining the work. This happens the more readily if the pressure be not sufficient. If the scraper or the stone is not uniform and even, it is very prone indeed to tear at the places subjected to the least pressure, because there, where the water has not been sufficiently squeezed away, the paper remains soft and fragile, while the pressure still is great enough to grip the fibres of the paper.
(c) Therefore the paper must be only slightly dampened if the color is very tough, partly to prevent tearing, partly to oppose no undue obstacle to the reception of the color.
(d) Paper dampened too much stretches in printing and produces uneven and dirty impressions.
(e) The quality of the water is not important so long as it is not dirty or putrid, in which latter case it may infect the paper and rot it.
(f) Just how much the paper must be dampened can be learned only from experience, because papers vary very much and in the case of sized papers it depends chiefly on the kind of sizing. On the average, we may calculate one wet sheet to eight dry ones in sized papers and one wet one to ten or twelve dry ones in unsized papers.
The following is the best way to dampen paper: Lay two or three dry sheets on a straight board. Then dip a sheet into water. Let the water drip off a little and lay the damp sheet carefully on the others. Now lay eight or ten dry sheets on top of this. Then put on another wet one and then eight or ten dry ones and so on till all the sheets destined for printing have been so piled up. Put over all a board weighted with a medium heavy stone plate. After half an hour increase the weight to several hundredweight or squeeze the paper in a press. Leave it thus at least twelve hours. Then it is generally ready for print. In aquatint it must be dampened more, about six dry sheets coming to one wet one.