A question that came up during
yesterday's live video is this: How is tube watercolor different from tube gouache?
Obviously they have similarities—they both have
gum arabic binder, they're both rich and concentrated in their pigment loads, and they can be used either transparently or opaquely depending on the properties of each pigment.
Is gouache always more opaque than watercolor? Is the pigment / binder ratio different? Is it supposed to be more matte when it dries?
To help shed light on these subjects, I asked two manufacturer's representatives to comment: Ann McCarthy of Winsor and Newton's Support Team, and Timothy Hopper, Executive VP of
Holbein, Inc.
1. Gurney: What's the difference between gouache and watercolor in their tube form?
Winsor and Newton: “Watercolor and gouache are similar in that they both are made with gum arabic binders. Designers gouache is considerably more opaque and this is done by loading additional pigment. While most colors in gouache are opaque, some colors, mostly transparent pigments, are semi opaque.
"The artist doesn't generally need to add white to most gouache colors to achieve opacity. The only caveats would be that gouache is susceptible to cracking when applied too thickly and that both types of media remain soluble even when dry, so layering can be difficult and we don't recommend varnishing."
Holbein, Inc: “The principal difference between Artist Watercolor (WC) and Designers Gouache (GC) is: Watercolor (WC) contains less pigment and more Gum Arabic, and Gouache (GC) contains more pigments and less Gum Arabic. As you know we (Holbein) are not adding any whitening agent to (GC) but we specifically choose (GC) pigments that are naturally matte.
2. Gurney: Is it advisable from your perspective if people use gouache as if it were watercolor (namely, in a transparent fashion), and watercolor in a gouache-like way, adding white to get opaque passages?
Winsor and Newton: “Watercolors are a traditionally transparent medium and usually applied in thin washes while gouache will be used when a more opaque color is desired. I suppose you could use them in ways they weren't intended for but it seems like a lot of additional work to turn a watercolor into a gouache and vice versa."
Holbein, Inc: If you add White to WC, it becomes opaque but your resulting color will become grayish in color."
3. Gurney: Is there any problem with using them together in the same painting?
Winsor and Newton: “Yes, they can be be used together."
Holbein, Inc: “It is common that WC and Gouache are mixed and used together in the same painting without any issue."
4. Gurney: Why is there a price difference between the two for the same pigment and same size tube?
Winsor and Newton: "Watercolor formulations are much more complex and cost more to make."
Holbein, Inc: “There has always been a price differentials between both gouache and watercolor. One of the main reasons is the production of Artist Watercolor is more detailed in nature than the production of Gouache. The same differential can be found in many high quality art lines."
----
Thanks to Mr. Hopper and Ms. McCarthy.