Most of my antique Welsh quilts were made with sateen and wool batting (or wadding) and I've found that when it comes to trying to reproduce the look of Welsh quilts, sateen is a good choice. Sateen is a type of weave and it sculpts over the batting (cotton or wool) when quilted which is why Welsh quilts made with sateen have such remarkable texture. Cotton sateen should not be confused with satin which usually shows up in a fabric store's bridal department. When looking for sateen in quilt shops, look among the solid colored bolts, that's where it usually is. Contact information for my local source will be listed at the bottom of this post.
Here are some bits of information about cotton sateen I can pass along to you.
Sateen is durable and washes well, care for it as you would any cotton fabric. Beware of using basting guns which push little plastic tacking pieces through the fabric, they will leave holes. Large safety pins can also leave holes, I alway thread baste. Machine quilting may also leave holes if you have to pick out stitches.
Sateen has an interesting quality because of how it's woven and reflects light. If you cut a piece of sateen in two, turn one of the pieces 90 degrees and sew them back together again and then look at them at an angle, one piece will probably appear darker than the other. Sometimes you won't notice this until you take a picture because the camera flash really brings out the effect. The gold quilt pictured below was pieced and I deliberately turned the pieces to see how the piecing would affect the overall effect when light hit the quilt just right (this was back in my mad scientist days).
Cotton sateen is a pleasure to hand quilt and is easy to stitch through but when you're stitching along the straight of grain, the stitches can seem small and irregular and again, this is the result of the way sateen is woven. My remedy for stitching on the straight of grain has always been to stitch with a very slight zig-zag which seems to keep the stitches from dropping down into the weave. Also, I don't worry about perfect stitches, with Welsh quilting patterns, people notice the effect of the patterns and overall design, not the individual stitches. I'm more interested in even stitches than perfect ones.
Cotton sateen makes great backgrounds for applique but because it frays easily, it can be a challenge when using it for the applique itself.
The gold quilt above also taught me another lesson about cotton sateen. The fabric on the back was regular (flat) cotton and I found that even though I had the quilt (sateen top, wool batting, flat cotton back) well basted, when the it was in a hoop, it felt like there were wrinkles on the backside of the quilt. I'd take it out and check that everything was smooth and all proper but back in the hoop the backing would'nt feel right. Again, I believe this is because sateen is woven differently than flat cotton and the 'give' of the two fabrics is different. My solution for mixing 'sateen fronts' with 'flat cotton backs' is simply to baste closer together, it takes a little more time but is worth it.
Another trait of sateen is how it discharges when something such as discharge paste or other color remover is applied. Black sateen usually discharges to a terrra-cotta color. I have a piece of navy sateen that discharges to a pretty pink. This may not be the sort of process that you'll use with Welsh quilting but if you're the mad-scientist sort of quilter, you may find a way to work it in.
Anyway, I really, really like cotton sateen and I've bought it by the bolt at times. It's out on the market but you may have to look for it. Extra wide sateen has been marketed to long-arm quilters so you might check out their sources. I've seen it at the big chain fabric stores but the quality was questionable, you'll get what you pay for. I've also had students who bought sateen sheets to use for quilts. My best current source for cotton sateen is GEE GEES'S QUILTING INC in Yelm, Wa. They have a website but the sateen isn't listed so contact them to see what they have available. They've been really good about keeping sateen in the shop as long as quilters keep buying it.
GEE GEE'S QUILTING INC
email - email@example.com
website - www.geegeesquilting.com