Paper Chase - On frog juice and other magic potions - part 1 of 1 2 3 4

by Mike McNamee Published 01/04/2004

Mike McNamee continues in his quest for paper perfection and makes a bit of a discovery on the way.

DEPENDING ON THE SIZE OF YOUR EGO, IT IS always mildly amusing to make a discovery, rush out to tell everybody about it only to have them say "Oh we have always done that". So it was with Giclee varnishes. As soon as we got stuck into the subject we found that the artists have been varnishing their work since Adam was a lad (well not quite that long) and have the process well under control.

Undaunted we carried on to see what we might add to the knowledge pool.

The problem

1. Fine art papers have a soft, easily marked surface

2. Matte Inks are a little powdery and can rub off and mark easily

3. The maximum density of inks on a soft art paper can sometimes only get down to 27% brightness value compared to as low as 6% for a gloss surface.

4. Images on matte surfaces can be a little flat and lacking in punch

5. Ozone and other airborne contaminants cause prints to fade faster

The uses of varnishes employ a number of terms to describe the changes effected by the coating, Typical are punch, pop, brightness, contrast and saturation.

The mission

We set ourselves the task of quantifying the effect by means of measurement. What, we wished to know was the effect on contrast, gamut size, saturation, black density, tone bias, white tone, uv absorption and surface toughness.

The method

We used the standard colour audit target as a basis along with an X-Rite DTP 41 strip reader and the Monaco Profiler 4.5 to generate both gamuts and profiles. The profile volumes were measured and compared in a freeware Java applet called ICC3D. An X-Rite Digital Swatch Book spectro was used to measure the spot values and also generate full spectral power distribution curves.

The test swatch file is described in Part 1 of Paper Chase. A test print was made using a bespoke profile developed specially for the ink, paper batches used. This print was then allowed to mature for an hour (sufficient for pigment ink but not enough for a dye ink - take note). The print was then measured an analysed. The test prints were then coated with varnish and allowed to dry. A rough quality check of the coating was made by examining it in uv light (see later).

To measure the gamut volume, 729 swatches were measured and input via the profile to ICC3D, which reports the volume and can also plot the gamut space visually as plain graphs or a 3D perspective plot.

The results

The visual effect of the varnish on a print is a very slight yellowing of the highlights, and a general darkening of the print. The matte finish produced a very slight change to the surface appearance. The satin and gloss finishes produced an increased depth in the blacks, an apparent increase in the saturation and an increase in the contrast of the print. Overall there was no detectable change in the colour properties of the print other than the darkening. On one of the canvas prints we coated, detail in the shadows which was not noticeable before coating suddenly became visible.

The gamut

Measuring the gamut volume is the work of several hours and so we limited our experiments. However on the tests we carried out, the gamut volume was increased by about 35%.The actual volume increased from 536,000 units to 727,500 units. To put these values in perspective we have compared some of the values obtained on other papers and inks as shown in the table alongside. From this it can be seen that the satin coating brings a matte paper up towards the gamut of a gloss paper.

The gamut comparison before and after varnishing is shown in the combination screen grab. The small balls lying outside the solid gamut area are those colour which have been created by the varnishing. The improvement is on all surfaces of the gamut although the main improvement is in the dark colours i.e. towards the bottom of the gamut volume shape.

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1st Published 01/04/2004
last update 21/07/2022 10:41:34

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