Transparent Red Oxide, or Pigment Red 101, is known by a host of names. I usually shorten it to TRO or even TOR which refers to another moniker, Transparent Oxide Red. In watercolor, it's also labeled as Mars Red, Venetian Red, Red Earth, Indian Red, English Red, and many more including Burnt Sienna. (Which is rather confusing because Burnt Sienna is usually PBr7. Oh well.)
Because of its hardy, lightfast, stable nature and superb mixing skills, PR101 has found its way into nearly every palette that I've featured—my limited 4-color and 6-color palettes, my 12-color travel palette, and my 18-color everyday, studio palette.
Since I've collected quite a few brands and colors of PR101, I thought a watercolor comparison might be helpful. Below, I'll sample various brands and colors so you can choose your favorite PR101, or ______________. (Fill in your color name of choice.)
I'll also showcase some common mixes, share a video so you can see how these colors appear in action and on different papers, and offer a Transparent Red Oxide mixing chart that you may download for free.
P.S. If you're new to watercolor and confused by the names and numbers, I have information on what all this means and how to decipher a watercolor label here. Please make allowances for monitor discrepancies. Article contains affiliate links.
PR101 Watercolor Swatches
Transparent Red Oxide is a beautiful brick red (literally—PR101 is used to color bricks) crafted from an extremely lightfast, synthetic pigment. Depending on how pigment and watercolor manufacturers treat it, PR101 will elicit a wide range of opaque to transparent colors that usually display little to no granulation.
I'm partial to transparent colors, so I mainly use the Transparent Red Oxide version, or Transparent Oxide Red or TRO or TOR... you get what I'm saying. But because I love this pigment so much, I keep several shades of this pigment close at hand. (In addition to the photo above, you can also see Transparent Red Oxide in every single landscape painting here.)
Below, in alphabetical order by brand, are a few of the many versions of PR101. All are single pigment colors, but feel free to check out the video to discover an interesting convenience blend.
When I first reviewed American Journey watercolors, I thought this brand's Transparent Red Oxide was a bit too orange and opaque for my tastes. However, I was continually drawn to this color, and now it's the premier PR101 in my palette.
It is powerful enough to give landscapes a serious punch of color, but it's also a willing and adept mixer and dilutes beautifully. This color is in the snowy landscape above, and I also love it for fall foliage, dry grasses, and deep sunset skies. Actually, I reach for it constantly and highly recommend that you give this version a try.
Oh by the way, AJ also makes another single-pigment PR101 labeled Indian Red. And yes, I'm very curious about it, so stay tuned!
Transparent Oxide Brown is simply another treatment of PR101, and what a glorious treatment it is! American Journey's version is a gorgeous warm brown and an excellent mixer. Add blue to gain a fabulous range of grays and blacks. A touch of Transparent Oxide Orange produces a substitute for burnt umber, or mix with white for a perfect mushroomy brown.
M Graham's Transparent Red Iron Oxide is the most transparent of this group, and its brown undercurrent reminds me more of a burnt umber than a TRO. This is the brand/color that was originally in my palette, and it's a stable color and excellent mixer that I have no qualms recommending. If you prefer a more understated, transparent PR101, MG's version could be an excellent choice.
This is a new color in my stash, but M Graham's Terra Rosa is quickly becoming a watercolor that I reach for often. To me, this PR101 embodies the rich Venetian reds that I remember studying in college. (For example, see Rembrandt's portrait of an old man in a hat.)
Terra Rosa is rather opaque and it can act finicky on some papers, but it dilutes and mixes well. I'll be experimenting more with this color, so if you try it, please leave me a comment and let me know what you think!
Rembrandt's Transparent Red Oxide is a solid PR101 color with excellent transparency. It behaves very much like a typical Rembrandt watercolor (see my review), possessing an extremely high flow rate and vibrancy. It's finicky on many papers and a bit difficult to control, but I've had no issues with it in mixes. In fact, it's one Rembrandt's more predictable colors.
If you're not confused enough, Rembrandt also produces two more single-pigment PR101s labeled Venetian Red and Light Oxide Red along with two PR101 blends labeled Permanent Madder Brown and Indian Red. Have fun with PR101's nearly unlimited choices!
Sennelier's Venetian Red was the first PR101 that I ever tried, and I drained the pan dry. Sennelier (pronounced Sin-Yay... I think) is probably the most opaque color in the bunch, but it's a lovely shade that strikes a nice, soft balance between orange and red. It's also extremely easy to rewet and a quality paint. If you like a high quality paint with quick and easy coverage, Sennelier's Venetian Red is an excellent option.
Video: PR101 Watercolor Brand Comparison
Transparent Red Oxide Watercolor Mixes
PR101 is an extremely stable pigment in mixes. Though opaque versions may muddy more easily (that's true with all opaques), I've had no issues with any of the brands that I've tried.
Transparent Red Oxide is a great "warmer" in a palette, and I love mixing it with other reds to heat things up. When mixed with blues and greens, it produces a massive range of earths, olives, and darks. Mixed with yellows, TRO will morph into a pleasing palette of oranges, terra cotta reds, and peaches.
Below is a chart of a few common Transparent Red Oxide mixes. I used American Journey's version because it's the one currently in my palette, but all will mix similarly. Though the swatches above are unalike by themselves, their distinctions fade in mixes, so pick a version that you like as a standalone color and have fun experimenting!