Dr. Ph. Martin's has been producing artist inks and liquid colours since 1934, and their range remains one of the most respected in illustration, calligraphy and fine art. With several distinct product lines, each formulated for different purposes, choosing the right one can be confusing. Here is what each line does and when to use it.
Radiant Concentrated Water Colour
The flagship product. Radiant inks are intensely saturated, dye-based liquid watercolours that produce vivid, luminous colour straight from the bottle. They are the go-to choice for illustration, comic art, airbrush work and any application where maximum colour intensity matters. Radiant colours are transparent, blend beautifully on wet paper, and can be diluted with water for lighter washes.
The trade-off is light-fastness — Radiant inks are dye-based and will fade with prolonged UV exposure. They are best for reproduction work (where the original is scanned and printed), exhibition pieces behind UV-protective glass, and any work not intended for permanent display in direct light.
Hydrus Fine Art Watercolour
Hydrus is the light-fast alternative to Radiant. These are pigment-based liquid watercolours with significantly better permanence — most colours rate excellent to very good on the Blue Wool Scale. The colour intensity is strong (though not quite as eye-popping as Radiant), and they handle similarly: fully intermixable, dilutable with water, and suitable for brush, pen and airbrush.
Choose Hydrus when the work will be sold, displayed or kept long-term without reproduction. The pigment-based formula also makes Hydrus slightly more opaque than Radiant, which can be an advantage or disadvantage depending on your technique.
Spectralite Private Collection Liquid Acrylics
Spectralite inks are acrylic-based — once dry, they are permanent and waterproof. This makes them ideal for mixed-media work where subsequent layers must not disturb the underlying colour, for outdoor signage, and for any application requiring water resistance. They work with brush, dip pen, airbrush and technical pen.
The waterproof property means Spectralite cannot be re-wetted and blended once dry (unlike Radiant and Hydrus, which remain water-soluble). Plan your application accordingly — work wet-in-wet for blending, and accept that dried edges are permanent.
Synchromatic Transparent Water Colour
Synchromatic inks are formulated specifically for transparent techniques — washes, glazing and layered colour building. They are less intense than Radiant but more transparent, making them the best choice when you need to see through multiple overlapping layers without muddiness. Popular with watercolour painters who want the convenience of liquid colour in bottles rather than pans or tubes.
Bombay India Ink
Bombay inks are opaque, waterproof, pigment-based India inks. They dry to a matte, velvety finish that is distinctly different from the glossy transparency of the watercolour lines. Bombay inks are the choice for calligraphy, lettering, comic inking and any application where opaque, flat colour is needed. The waterproof formula means they can be painted over with watercolour without smearing.
Iridescent Calligraphy Colour
Iridescent inks contain fine metallic particles that shimmer and shift colour under the light. They are designed for calligraphy, decorative lettering, card making and any project where a metallic or pearlescent effect is wanted. They flow well from dip pens and brushes but should not be used in technical pens (the metallic particles can clog fine nibs).
Tech Drawing Ink
Formulated for technical illustration, architectural drawing and precise line work. Tech inks are waterproof, opaque and designed to flow consistently through technical pens. They dry to a dense, matte line with excellent edge definition.
Choosing the right line
For maximum vibrancy (reproduction work, illustration): Radiant. For light-fast fine art: Hydrus. For waterproof mixed media: Spectralite. For transparent layering: Synchromatic. For opaque lettering and inking: Bombay. For decorative metallic effects: Iridescent. For technical drawing: Tech.
