It first and most importantly depends on the fragility of the piecework. If very delicate, conservators use Orvus paste and minimal agitation and water temp.
Most vintage piecework can tolerate more aggressive treatment. Many people have had good luck with using Biz. I prefer to use Shaklee Nature Bright. Though its not as readily available as Biz, you have to order from their website or a distributor. If the linen is white don't be afraid to use hot water and let it soak for a couple of days, changing the solution in between, as oxygen bleach loses its efficacy pretty quickly. I also use two scoops to half a bucket of water. Rinsing is very important. I rinse a couple of times in running water before washing in the washer on delicate with detergent and more Nature Bright, on hot if white. I rinse til clear, at least three or four times. Sometimes I'll put vinegar in the next to last rinse to help remove soap residue.
Never use chlorine bleach on vintage linens, it compromises the integrity of the fabric and can react with the minerals in the water and yellow the fabric.
I try to use a pretty neutral detergent. Meaning, not allot of additives to it. I like Shaklee powder or Cheer powder. Optical brighteners tend to change the hue of vintage linens, so good to limit the amount in your washing solution. Biz has quite a bit added, Nature Bright and Shaklee powders are more limited. Cheer powder has none added.
Line or lay flat to dry. Do not dry in the dryer, ever. I store mine unironed, starch causes yellowing over time. Often the yellow spots we see on vintage linen is starch or food residue that's been redeposited from inadequate rinsing.
Good luck, it's labour intensive, but te results are worth it.
Todd