handprint : drying shifts
 

watercolor drying shifts

 
It's well known that watercolor paints change color appearance as they dry, but no art reference has published reliable information about these changes — until now.

Why Do Shifts Occur? A detailed explanation of paint color shifts is given in the page on the secret of glowing color. Briefly, color is created because a pigment absorbs some light wavelengths and reflects others. However, some light at all wavelengths (white light) is always scattered at any surface boundary between two substances that have different refractive indices or light bending abilities. Many substances, including paint pigments, have a similar refractive index to water, so wet paint appears to have a rich color because scattered white light is minimized. When watercolor paint dries, however, the water evaporates and leaves the paint in contact with air, which has a much lower refractive index than pigment. This causes more white light scattering at the pigment surface, which mixes with the reflected pigment color to make the apparent color appear lighter and duller.

Paint Measurements. The table below summarizes the drying shift in mass tone color appearance for 75 of the most commonly used watercolor pigments or convenience mixtures. The shifts were measured as the difference in masstone color appearance as measured with a GretagMacbeth Spectrolino spectrophotometer when the paints were at a satin wetness and again after they had dried for one hour; the tabulated results are the average of measurements on two separate samples of paint. The color shift is shown as separate changes in lightness, chroma, hue angle, and as the total color shift:

• L or lightness is measured from 0 (pure black) to 100 (pure white); a shift of 10 equals one step on a 11-step value scale; a minus sign means the paint became darker. The average shift in L is only 2.3.

• C or chroma is measured from 0 (pure gray) to 100 or more (high chroma); a minus sign means the paint became less saturated (duller). The average shift in C is -10.7; this loss of chroma is the main cause of the drying shift in watercolors.

• h or hue is measured in degrees of the CIELAB a*b* plane, with 0 at magenta and 90 at yellow. The average shift in h is -2.9: as they dry, most colors shift clockwise on the CIELAB a*b* plane or counterclockwise on the artist's color wheel (yellow toward red, blue toward green).

• Total Shift is the combined (three dimensional) change across L, C and h; this is the total apparent effect of the drying shift. The average across all paints is 12.9.

Color shifts are highly variable — they depend on paint vehicle, dilution and application method — so use this table as a rough guide. Even so, it's clear that drying shifts are not limited to a lightening of the paint, as usually claimed: over one third of the pigments listed here actually darkened! The consistent change is that paints lose chroma as they dry (see diagram at right); sometimes large hue shifts occur as well. All of these shifts combine to make up the total change in color appearance.

In the guide to watercolor pigments, the total drying shift is reported in terms of the percentage change in lightness, chroma or hue angle. An equal lightness or chroma change will appear larger in darker or duller paints, because they have so little lightness or chroma to begin with.

This table lists pigments by increasing shift in chroma (C). The links below allow you to see the data sorted by increasing changes in L, h, total shift, percentage total shift, or listed alphabetically by color index name.

Sort by: Lightness Shift • Chroma Shift • Hue ShiftTotal ShiftTotal Shift %Color Index Name
Watercolor Paint Drying Shifts
CI NamePigment/Paint NameBrandShiftTotal
LChShift
.naples yellow Winsor & Newton-2.98.8-2.39.4
PBk9ivory blackWinsor & Newton13.31.57.513.5
PBk7lamp blackWinsor & Newton16.21.532.116.2
.sepiaWinsor & Newton10.30.23.110.3
PY53nickel titanate yellowWinsor & Newton-2.9-0.9-2.85.9
PY184bismuth yellowWinsor & Newton-1.8-2.0-2.63.5
PBr24naples yellow deepWinsor & Newton-4.4-2.1-4.95.8
PY35cadmium lemonWinsor & Newton-1.9-2.3-2.74.0
PY154benzimidazolone yellowWinsor & Newton-0.8-2.3-1.33.6
PB36cerulean blueWinsor & Newton0.0-2.30.02.3
PV14cobalt violetHolbein8.4-2.32.310.7
PY3 hansa yellow lightDaniel Smith-1.8-3.5-1.44.1
PBr7raw umber [dark]Daniel Smith7.7-3.7-2.78.5
PBr7raw umber [light]Winsor & Newton1.1-4.2-0.84.6
PG50cobalt green YSWinsor & Newton-2.9-4.3-1.25.3
PB60indanthrone blueWinsor & Newton8.7-4.7-7.010.2
PG50cobalt green BSWinsor & Newton1.2-4.9-2.15.2
PV15ultramarine violetWinsor & Newton1.7-5.1-0.95.8
PG50cobalt teal blueWinsor & Newton1.4-5.1-0.55.4
PY43yellow ochreWinsor & Newton-0.3-5.6-1.66.0
PY153nickel dioxine yellowWinsor & Newton-0.7-5.9-1.86.2
PB72cobalt blue deepWinsor & Newton3.5-7.3-1.98.2
PY42gold ochreWinsor & Newton0.7-7.6-0.38.7
PV16manganese violetWinsor & Newton3.8-7.80.98.6
PB36cobalt turquoiseWinsor & Newton0.1-8.9-2.99.5
PB17phthalo cyanHolbein7.3-8.9-2.711.6
PBr7burnt umberWinsor & Newton4.5-9.3-2.510.5
PB27prussian blueWinsor & Newton11.4-9.3-11.315.2
PR112naphthol redHolbein-0.8-9.4-2.69.8
PV19quinacridone redDaniel Smith1.2-9.6-3.49.9
PV19quinacridone roseWinsor & Newton0.8-9.7-1.89.9
PV23dioxazine violetWinsor & Newton7.7-9.8-1.414.0
PG7phthalo green BSWinsor & Newton6.4-10.1-2.112.8
PB15:3phthalo blue GSWinsor & Newton6.9-10.4-5.312.7
PR88thioindigo violetWinsor & Newton4.2-10.5-0.211.5
PR N/Aquinacridone carmineWinsor & Newton0.9-10.5-3.510.8
PB28cobalt blueWinsor & Newton6.5-10.7-2.912.7
PO20cadmium orange [mixed]Winsor & Newton-4.1-10.7-8.513.5
Average2.3-10.7-2.912.9
.permanent green lightMaimeriBlu0.8-10.9-1.411.0
PR209quinacridone redWinsor & Newton0.6-11.0-3.911.4
.sap greenWinsor & Newton9.3-11.8-0.216.2
PBr7venetian redWinsor & Newton0.3-11.9-5.312.1
PV19quinacridone violetWinsor & Newton5.3-11.9-4.113.2
PR122quinacridone magentaWinsor & Newton4.6-12.0-5.113.2
PG17chromium oxide greenWinsor & Newton-6.2-12.14.913.6
PY97hansa yellowDaniel Smith-2.0-12.2-3.912.9
PR255pyrrole scarletDaniel Smith-0.3-12.6-5.013.3
PBr7burnt sienna [dark]Daniel Smith3.7-12.7-4.213.4
PG36phthalo green YSWinsor & Newton6.3-12.8-2.514.6
PR108cadmium scarletWinsor & Newton-2.0-13.0-6.914.2
PR254pyrrole redWinsor & Newton-0.1-13.1-4.613.6
PB16phthalo turquoiseMaimeriBlu7.4-14.04.615.9
.hooker's greenDaniel Smith7.1-14.2-3.015.9
PY150nickel azomethine yellowDaniel Smith-0.9-14.3-2.314.4
PR188naphthol scarletWinsor & Newton0.3-14.5-5.315.2
PBr7burnt sienna [light]Winsor & Newton0.0-14.5-2.914.6
PB15:1phthalo blue RSWinsor & Newton9.2-14.7-5.917.6
PR171benzimidazolone maroonDaniel Smith10.0-15.40.118.4
PB29french ultramarine blueWinsor & Newton7.3-15.8-4.117.7
PY65hansa yellow deepDaniel Smith-1.6-15.9-4.716.7
PY35cadmium yellow deepWinsor & Newton-4.7-16.2-10.719.2
PR170naphthol redDaniel Smith0.9-16.5-6.317.2
PO62benzimidazolone orangeWinsor & Newton-1.0-16.6-5.217.3
PR206quinacridone maroonWinsor & Newton2.3-16.7-5.017.2
PR108cadmium redDaniel Smith1.2-16.9-7.017.7
PY35cadmium yellowWinsor & Newton-4.5-17.3-7.519.2
PR176benzimidazolone carmineDaniel Smith3.8-18.0-6.418.8
PO49quinacridone goldWinsor & Newton-1.5-18.1-4.718.5
PR177anthraquinoid redDaniel Smith4.5-18.1-6.619.1
PO43perinone orangeDaniel Smith-1.8-18.2-7.019.2
.permanent greenDaniel Smith3.0-18.2-3.818.6
PR178perylene redDaniel Smith2.4-19.3-6.519.9
PO20cadmium orange [pure]Daniel Smith-2.0-19.3-8.120.7
PR179perylene maroonWinsor & Newton5.1-20.4-3.121.0
PY129green goldWinsor & Newton-0.4-21.6-3.421.7
PR149perylene scarletDaniel Smith5.4-21.6-7.422.7
PR108cadmium red deepUtrecht-0.5-21.8-9.422.5
PO48quinacridone burnt orangeDaniel Smith4.5-22.2-4.622.8
Sort by: Lightness Shift • Chroma Shift • Hue ShiftTotal ShiftTotal Shift %Color Index Name

 

Last revised 08.01.2005 • © 2005 Bruce MacEvoy