Artist's Inks - Pigment vs. Dye
Inks are a very diverse family of art materials. There is an ink for every purpose it seems, so how does one determine which is the right ink for the job?
We intend to answer some of the more common ink-related questions:
- What is the difference between pigments and dyes?
- What actually is a pigment/dye?
- How does it work?
- Which ink is waterproof?
- Can I use this ink in my fountain/technical pen?
What are inks?
Inks are colour (either pigments or dyes) suspended or dissolved in a thin vehicle (a liquid) and contains a binder (a substance that holds everything together)
Some common binders
- Shellac: makes ink water-resistant when dry
- Acrylic emulsion: makes ink waterproof when dry
- Gum Arabic: adds sheen, increases film flexibility, and makes the ink re-wettable even after drying
Question 1:
Mud vs. Kool-Aid
The easiest way to explain the basic difference between pigmented inks and dye based inks is take you back to high school chemistry class: Solutions vs. Suspensions.
Imagine a mud puddle; There is silt and dirt and organic matter suspended in the water. If the puddle is left undisturbed, in time the particles will settle out of the water and collect in a layer on the bottom. Chemically, this is called a suspension. Pigmented inks are a suspension.
Now imagine Kool-Aid; If you mix a spoon full of Kool-Aid into a cup of water, the Kool-Aid sugar crystals will completely dissolve into the water. If you place an airtight lid on the mixture (to avoid evaporation) and let the cup of sugar-water sit on the shelf (even indefinitely) you will never, ever see a layer of sugar particles settle on the bottom of the container. Chemically, this is called a solution. The sugar (solute) is dissolved in the water (solvent) to form a solution. Dye-Based inks are a solution. (And you thought you’d never need to use high school chemistry again!)
Question 2a:
What is a Pigment?
Dry pigments are used to create all artist quality paints. Pigments are generally composed of solid matter (rocks, minerals, metals, charcoal, etc ) that have been ground to a powdery talc-like texture. Pigment powder is then mixed with a specific vehicle (or carrier) to create paint or ink (oil for oil paints, acrylic polymer emulsion for acrylic paints, gum arabic for watercolours, etc...). Relative to dye particles, pigment particles are much, much larger.
Adding powdered dye to water to make a dye solution
Question 2b:
What is a Dye?
Dyes, are coloured chemicals that are either a liquid themselves or in the form of powder that is easily dissolved in a liquid (be aware that not every dye is water-soluble). Our ancestors made dyes from many natural materials such as bark, nutshells, berries, roots and even insects. Many modern dyes are synthetic and offer brighter, deeper and longer lasting colours. The primary issue with dye is that many colours are not considered to be lightfast. This means that many dye colours are not stable under direct exposure to light (especially sunlight) and will fade, sometimes quite rapidly! While this is also true for some pigmented colours, it's the exception rather than the rule.
Question 3:
How does it work?
Pigmented Ink
When a pigmented ink is applied to a substrate (meaning your paper, canvas, board, or whatever) the ink will will lay on top, forming a film on the surface of the substrate. Pigment particles can sometimes get trapped in the texture of the substrate, creating something like a staining effect (in much the same way that dirt will get ground into the knees of your jeans). The pigment particles become physically trapped in the fibers, which is not the same as being chemically bonded to the paper. With pigmented ink, it's the binder (or vehicle) that is responsible for making the pigment stick to the substrate.
Pigment Opacity/Transparency: Most pigment based inks and paints are somewhat opaque in nature. Because pigment particles tend to accumulate on the surface of the paper (as opposed to soaking-in) pigment provides more opaque coverage than a dye. It's worth noting that some pigmented colour formulations have a staining effect; this is due to the pigments used having dye properties (meaning that they partially dissolve in the vehicle liquid).
Dye-Based Ink
Being a solution, dyes will readily soak-in and attempt to chemically bond to the substrate, becoming one with the substrate. Some dyes may include another ingredient called a mordant which allows the dye to create a permanent chemical bond with the paper. If you’ve ever dyed fabric you'll know that certain types of dyes only bond chemically to certain types of fibers; Keeping this in mind, if you want to have more control over the permanence of your dye (either more or less permanent) try changing the substrate you're using (ie: changing to a cotton rag paper like Stonehenge for more permanent bonding, or a synthetic paper like YUPO for less permanent bonding).
Dye Opacity/Transparency: Most dyes are inherently transparent or translucent. (A transparent film is so clear you can see through it to lower layers without losing detail. A translucent film allows one to see through to lower layers somewhat but with significant diffusion, distortion, and the loss of detail.)
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Question 4:
Which inks are water-resistant?
- Water resistant implies that the ink is not prone to smudging after drying unless it is soaked or scrubbed
- Waterproof implies that the ink is 100% smudge proof after drying and will not smudge regardless of soaking or scrubbing
We tested these pigmented inks to see which ones are actually water-resistant...
Front Row L to R: Winsor & Newton Drawing Ink (Black India), Royal India Ink, Daler Rowney FW Acrylic Ink, Pen & Ink No-Shellac India Ink
Back Row L to R: Zig Brushables (Pure Black), Faber Castell Pitt Pen, Staedtler Pigment Liner, Sakura Pigma Micron
I laid a squiggly line of ink on linen textured cardstock and allowed it to dry 24 hours. I then tried to smudge the ink squiggle with a generous application of water and some gentle scrubbing with a soft brush.
(click to enlarge) Winsor & Newton Drawing Ink seems to be the most waterproof, however the manufacturer is candid about the fact that only the Black, White, Gold, and Silver inks are pigmented and waterproof. All other colours of Winsor & Newton Drawing Inks are not considered water resistant (!)
The permanence of Dye-Based Inks will depend on the vehicle used
- Water-based dye solutions are not water-resistant; they will run and smudge with the application of more water unless a mordant is added.
- Alcohol & Solvent-based dye inks (such as Sharpies) will not run or smudge with the application of water.
These are the dye inks we tested..
Back Row L to R: Cross Fountain Pen Ink, Jacquard Pinata alcohol Ink, Winsor & Newton Drawing Ink (Blue)
Font: ShinHan Touch Twin Alcohol Marker
The test was the same process as above; Here are the results:
(click to enlarge) The alcohol-based inks didn't budge, but the water-based inks were easily reactivated.
Question 5:
Can I use this ink in my fountain pen or technical pen?
The short answer is "probably not". Most pigmented inks will permanently ruin a fountain or technical pen in just a single use, so filling your pen with the correct ink is pretty important. The best decider is to read the product label. If the label doesn't specifically say that it's intended for use in pens, then don't risk it.
Of the products featured here, only Cross Fountain Pen Ink, Pen & Ink No-Shellac India Ink, and surprisingly several colours in the Daler Rowney FW Acrylic Inks indicate that they're safe for use in pens.
A Final Note of Caution
When in doubt about a specific ink, or how it responds on a specific substrate, do yourself a favor and DO A TEST first.... Before you learn the hard way that Pigma Micron pens wipe off Yupo paper like a whiteboard!
If that sounds suspiciously specific, it's because it is; that was a hard truth that I learned the hard way while doing a time-sensitive commission piece. An entire 3 person portrait wiped off the Yupo, I cried and started from scratch... 8 hours of work lost.