This "solid color tartan" (for lack of a better term) was first dreampt up by the folks at House of Edgar woolen mill. They produce their Dark Isle tartan in black (most popular), navy blue, and I beleive I have seen white. Black and navy are the only two colors listed on their stock list. They produce it in a 13 oz (medium kilt weight) cloth.

The technique is possible using a Jacquard loom, which allows the weaver to create a tartan pattern using the same color yarn. Here is how the Scottish Tartans Authority (STA) describes the process:
"An ecru (white) yarn has been woven on a Jacquard loom with the sett being formed by stitches other than 2/2 twill and then the finished fabric has been piece-dyed black. The sett is highlighted because of the differing light reflecting qualities of the stitches."

The STA even had to come up with a new category of tartan for these designes, called "solid sett tartans" (cloth of a solid color, but with a visible tartan sett pattern).

Some people have mistakenly attributed this effect to the use of two slightly different shades of black yarn being used (such as the House of Tartan), but this in inaccurate. As you can read in the STA notes, the whole peice is dyed as a whole. In fact, if you look at the fabric straight on, all you will see is a solid black peice of cloth. It is when you look at it from an angle that the tartan design appears.

As I said earlier, House of Edgar was the first mill to create such a tartan, which they called Dark Isle. Others followed, as the concept proved popular. Lochcarron makes a 13 oz cloth called "Dark Douglas" (because the sett used for the pattern is taken from the Douglas tartan). Marton Mills has a version called "Black Isle."

Many here on X Marks will be familiar with Stillwater kilts "Nightstalker" tartan. I haven't seen it in person, but I don't know if this truly qualifies as a "Solid sett tartan," because in the description it is referred to as a "black and grey" tartan, implying that two different colors of yarn are actually used in producing the cloth, which would make it a traditional multi-colored tartan.

Anyway, the solid sett tartans are a new idea, the Dark Isle tartan first being developed in 2003, and the others following after. They are all considered fashion tartans, of course. Whether this is a fad or a lasting fashion will be determined by how popular the concept remains in the years to come!