This lovely star quilt came to me to patch a couple of places with brown stains. It serves as a wonderful example of how hard it is to match old whites.
Old whites are virtually never pure white. This is both because the original fabrics may never have been as white as ours today because they didn't go through the same intense bleaching processes. And then, they have aged, with varying degrees and combinations of browning, yellowing, and greying.
Here are the two I found that are closest to the original fabric. You can see that even rearranging them changes what they look like. These two photos were taken by daylight, an overcast day.
Matching whites (and any color, really) gets even trickier if you also look at the fabrics in the evening under artificial light. Incandescent bulbs lend a distinctly yellow overtone to everything. So yellowed whites appear even yellower. Halogen lights and full-spectrum lights, which is mostly what I have in my house, still make colors look different than daylight.
This photo was taken under artificial light. I altered it a bit to bring out the yellow like incandescent lights do.
When I'm choosing fabrics, I always look under both lightings, and try to pick fabrics that give the best average effect. In this case, I also had to consider the texture of the yellower of these two fabrics, which has a rougher weave. The older cottons were woven with finer threads than some cottons, especially the Kona brand, are today.
Whenever I have trouble deciding between two not-quite-right fabrics or not-quite-right threads, I nearly always opt for the one that errs to the dark rather than to the light. It will blend in as a shadowed piece, rather than shining out as too light. So in this case, I chose color over texture.
Here is the full quilt, in all its glory. Another post on this quilt is here.