Saturday, July 28, 2012

Queensland 1 shilling mauve worn plate / ink buidup

I have many examples of this issue where the frame line dots are especially worn or ill-defined. The colour is almost always the bright mauve or deep mauve shade. The dated copies include October 1890, 1891, April 1892, November 1893 and June and September 1895. All of them are perf 12, watermark 6. Here are some representative examples.















Postscript: I had assumed this was a worn plate. However it doesn't fit because it occurs only in this colour over a long time period. If it was a worn plate it should only occur in one time frame before being repaired or replaced. Then I read an article by Gordon Monk et al on compartment line research relating to the Australia 1d red George V issue. Here is a relevant extract:


Surface printing is notorious for a problem called ‘ink build up." Printer's ink is basically a bonder such as linseed oil. Pigments (usually in powder form), additives, such as “brighteners” and solvents. It is the solvents that are the main culprit for the problem of ink build up.

Printer's ink contains solvents in order to create the right viscosity. The viscosity allows the ink to be deposited evenly and at the right thickness on the plate and must have sufficient liquidity to be transferred from the plate to the paper. Once the sheet is printed and dropped in a receiver tray, the print must be dry enough not to cause a "kiss print" on the back of the next printed sheet. It is at this point that the solvents play another role. They must have evaporated sufficiently for the ink to be "dry" enough before the next printed sheet drops. The time span between printed sheets also applies to the ‘inking up" of the plate. After the printed sheet is removed from the plate, very little ink is left on the plate, but what remains is relatively dry. Some of the ink is deposited over the edge of the printing surface and not “picked up" by the paper. 


When the plate is inked again a new layer of ink is applied over the previous deposit that is again not picked up by the paper. As the solvents evaporate, layer after layer of ink is deposited on the edges of the printing surface and the end result is loss of definition. The spaces between the shading lines become smaller up to the point that they fuse together. It takes many applications of ink for the loss of detail to become noticeable; however, when it does the process seems to accelerate.


And this is what appears to have happened. I would suggest that the reason it only occurs with this particular colour shade is due to the specific combination of pigments that make up this particular colour shade.

Here is an extreme example

No comments:

Post a Comment