Paper Chase - On frog juice and other magic potions

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 Giclée 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.

Profile

The Highlights

The effect of the varnish is to depress the highlight tone from 95.79% to 93.64% i.e. on the order of 2%.This is detectable and if the spectral response is measured then the uv peak at 400nm has been chopped off. This has the visual effect of removing some blue from the white tone which makes it look more yellow if the coated and uncoated materials are compared side by side. It is actually made more neutral, it moves from Lab coordinates of 1 -3 (i.e. blue) to 0, - 1 (i.e. less blue).

The Mid Tones

The mid tones are depressed by 4.5% for the matt varnish, 6.5% for Satin and 7.1% for the gloss.There is no visually discernable change to the colour of the greyscale and spectro results indicate a shift from green bias to redmagenta moving from ¾ tones to ¼ tones.The varnish does not change this shift.The bespoke profile made for the testing produced a near perfect neutral as a starting point. Gamut volumes with coating

The Shadows

The Dmax values are shown in the table. This is the nub of the improvement - the linearity is straightened and the roll off in the toe is eliminated. The brightness value is dropped ffom around 17.8% (which is quite good) to 8.5% (which competes with gloss and lustre papers. Thus the improvement from the use of the varnishes is considerable. The difference between the matt and either the Satin or gloss results are readily discernable by eye, the densitometer reading confirm the results. The value of 2.08 from the gloss varnish is up with the best achieved on photographic silver halide prints.

The Tone Contrast Curve

In order to put some order to our measurements, a strip of three graduated grey scales was made onto the same piece of paper. This was measured before varnishing and then each strip was given two coats of either Matt, Satin or Gloss varnish, checked for coverage in uv light, allowed to dry and then remeasured. The results were plotted as shown.

They indicate that there was a slight lightening in the blacks due to the matt varnish but significant deepening of the shadows with both Satin and Gloss varnishes. This is reflected in higher Dmax values and the smaller Lab brightness reading. The highlights moved very slightly lower in density for all varnishes. With the satin and gloss varnishes the mid tones were depressed and the shadows depressed yet further. This is effectively an increase in contrast depending on how you do the sums it is of the order of 7% to 10 % change. The curve shape in the shadows is most affected as the toe is straightened.

The results would suggest that if you wish to preserve your tonal balance exactly you should lighten your mid tones by about 5% and reduce your contrast by a similar amount. Alternatively you could accept the extra zip in you print and rejoice in it! The Rolls Royce alternative is to make a profiling target and to build a profile specifically for a varnished workflow. We tried this but the results were a little inconclusive - certainly not worse, but not significantly better either. It is rigmarole to perform this operation and so we only attempted it the once! We did however straighten out the linearity tone curve somewhat and bring the tones to the target values.

Grayscale Summary of data

The Colours

There was a measurable increase in the saturation of the tones in the yellow-red quadrant of the gamut. However, with a perceptual rendering intent the effect was diluted as you move towards the neutrals and so the effect on the lighter skins tones was barely measurable. In any event the changes were not particularly noticeable in typical skin tones There was a very slight rotation of the hue angle towards yellow in the skin tones presumably because some blue form the OBA's had been filtered out.

The overall colour error on the Macbeth chart set of 24 colours was made worse by the application of the varnish mainly due to the darkening of all the colours. This can be seen in the tables in all the lightness channel errors.

Surface Strength

The robustness of the surface was massively increased. The particular paper and ink combination that we tested is very sensitive to marking. Careless rolling up of a print (when the edges are allowed to touch the printed surface) can be enough to ruin a print. After coating you can drag a fingernail across the surface with considerable force and not do any damage. The surface may be rubbed with the moistened ball of the finger as hard as you like, with no effect.

UV and Moisture protection

This is a tricky one to call. There is no doubt that the uv properties of the surface are radically changed, apparently for the better. How good the surface is at keeping water vapour and ozone out in unknown. However it is pertinent to recall that the varnishes were originally developed to protect signboards, which are traditionally exposed to the full force of the elements. Degradation of the varnish under ultra violet light is also not quantified. The balance of probability is that the varnish will significantly improve the all round durability of the print or canvas.

The one thing, which is certain however, you should test the products on a scrap print before you apply it to you masterpiece. You need to be sure that your ink/paper combination is compatible, as well as acquiring a bit of skill in the process.

Let's Look at Real Pictures

We had got a little blasé about all the above and so we hauled Tom Lee round with some examples of his latest ventures into renaissance style, low key portraiture. His face was a picture as we slopped the varnish over his Ilford Canvas. Flowers deep in the shadows of the background had vanished on printing, but came back into bloom with the application of varnish - it really was quite a stunning effect. Tom was pretty stunned too - he went off to buy some! Digital artist, Carol Tipping was equally impressed, we sent her off with a borrowed tin of the satin product to complete her own series of tests. Many artists are applying the varnish in an "uneven" brushing which is sympathetic to the underlying brush-mark structure of the original. Don't try that one at home unless you are an artist - it's harder to do than people like Carol make it look!

PRICES AND CONTACTS:
DCP Varnishes £24.95 for 750ml
Purdy Brushes 2” £12.26; 2.5” £14.13; 3” £17.54.
DCP Systems 0114 257 3640
LG Harris 2”White Diamond £4.67
Mini Roller Handle £1.27
Foam Mini Rollers 72p
Harris products are available from all good hardware
stockists
LG Harris Customer Service 01527 575441
ALL PRICES ARE EX VAT

“Overall then this material is one of the more exciting things to come past our desk for some time…”

Paper chase

There are a number of ways of applying a Giclée varnish namely:

Brush

Synthetic roller

Sponge roller

Spray

Silk Screen

Paperchase

The top image shows one of our early, rather clumsy attempts including all the drops spots and brush marks - it looked quite good at first as well! DCP recommend (and sell) the Purdy brush. These are the top dogs of the painting world and they certainly do perform well. If looked after they should last a lifetime. We got our best results brushing in one direction and then brushing off finally in the other direction. Two coats always produced a better result than one, no matter how much care we took with the first coat.

ClearStar, another of the manufacturers of varnishes do not recommend bristle brushing at all for their product (reviewed last issue) - they go for roller application. We only got a half decent result using a cheap 4" x 1 ¼" roller with a sponge surface but suspected that a higher quality one would have produced a better result. LG Harris are a big name in brush and roller making and so we contacted their helpful consumer division and obtained samples of high quality brushes and rollers. Their catalogue shows 22 pages of brushes, pads, rollers and dishes so we took their advice and went for a 2" White Diamond, professional quality, bristle brush and one of their small high-density foam rollers. While it was immediately apparent that the high-density foam rollers were much superior to the cheap ones we purchased at the local hardware shop, foaming under the roller was a problem as it left pit holes all over the surface. The spread of the coating was however more even this way and we experimented with roller application followed by brush smoothing with the Harris Diamond. To some extent the jury is still out on this one. An uneven first coat is still visible after a second coat has been applied. Both Carol Tipping and DCP favour three coats (although this visibly thickens the surface texture).

Apllying varnish Subsequent discussions with fine art publishers led to the suggestion of rounding the edges of the foam roller to assist in blending the different roll strokes as the varnish is applied. This too is a method which will bear some more experimentation

Coating canvas is much easier than the flatter, plain surfaced materials, the natural undulations of the surface tend to hide any imperfections in your brushing technique.

A tip for users - you are going to need quite a lot of clean paper to place your prints on as you apply the varnish. Newsprint will not do the job, it is far too dirty and sheds ink. Costco sell 100m rolls of white banqueting tablecloth paper, which proved to be ideal and very inexpensive (£8.21 per roll) - or nick the remnant from your next wedding!

CONCLUSION Overall then this material is one of the more exciting things to come past our desk for some time.The opportunities for the social photographer are seemingly endless.The delicacy of art papers and matte black inks has always meant that they have to be put behind glass to afford a sensible level of protection.This is not desirable if you wish to show off the texture of the paper, something that artists and art lovers are sensitive to. Similarly for canvas prints from inkjets - they look a bit naff behind glass, oil paintings are nearly always varnished and displayed open, within a swept frame. Giclée varnishes are a magic goo which assists at all levels. And what of Frogs? Well Frog Juice is the material used by sign makers to protect their painted signs. There is a solvent-based varnish, which might have applications for dye based ink jet printing. Sadly froggy had gone a' courtin' and no samples were provided for test - another day perhaps!

applying the varnish

The SWPP 2008 Convention was an outstanding success,
we have 130 days to get ready for the 2009 convention - which starts on January 14, 2009

Photo Quote: Does not the very word 'creative' mean to build, to initiate, to give out, to act - rather than to be acted upon, to be subjective? Living photography is positive in its approach, it sings a song of life - not death. - Berenice Abbott American Photographer, 1898-1991