All About Aurifil, Part 2

Welcome to the second installment of our All About Aurifil series! We had so much fun last week and loved seeing all of your responses. We’d like to continue your “threaducation” with some information about “Indanthren” and “Reactive” colors as well as our 40wt & 50wt threads. Let’s turn attention once again to our Technical Creative Specialist, Kristi, for All About Aurifil!

Click here to view the full brochure

If you have one of our thread color cards, you’ll see a page dedicated to the washing instructions. I know that it’s typical to buy your supplies, make a quilt, and throw it in the wash like you would with anything else — well, maybe with a little more care than everything else, but you know what I mean — you may not always consider particular care for the fabric or the thread. You think about the quilt as a whole… once the quilt has been made, you’re really only concerned if the colors of the fabric will bleed. But, did you know that there are proper washing instructions for different colors of threads?

Aurifil has 23 Reactive Colors (marked with a * on the color chart), 211 Indanthren Colors, and 36 that are Multicolor (our variegated threads, marked with a small black square.)

Reactive dye is a type of deeply colored organic material that attaches itself through a chemical reaction. This chemical reaction forms a molecular bond between the dye and the fiber. The dye then becomes a part of the fiber and is a lot less likely to “bleed” like something would that was dyed by simple absorption. It is recommended to launder our Reactive Color threads without bleach, tumble dry in cool air, iron on a low heat setting – no more than 300˚F (150˚C) – and machine wash in cold water – no more than 140˚F (60˚C).

Indanthren Colors are our ‘work-horse’ colors. They are seen as more heavy-duty and have a high level of colorfastness. “Indanthren” is a trade name for the first synthetic vat dyes, discovered in 1901 by a German chemist named Renohn. Vat dyes are insoluble in water, mainly used for cellulose or protein fibers (plant or natural fibers like cotton, flax, or wool), and have a final color that is developed in the oxidization process. Indanthren dyes can withstand light, bleach, and somewhat higher temperatures. It is recommended to launder our Indanthren Color threads in a maximum washing temperature of 160˚F (70˚), iron no hotter than 300˚F (150˚C), bleach in cold water only, and use a dryer set at low or no heat.

Our Multicolor threads are also known as our variegated threads. They are marked with a small black square on the color card. It is recommended to launder our Multicolor  threads in a maximum washing temperature of 85˚F (70˚), iron no hotter than 230˚F (150˚C), without bleach, and use a dryer set at very low or no heat. For more information about our variegated threads, keep an eye out for a guest post at the end of this month!

It’s important to keep these things in mind when sewing a new project, especially if making a gift. I like to include a notecard with laundering instructions when I gift a handmade sewn item, a lovely and often perfect final touch!

So, now let’s talk about everyone’s favorites: 40wt & 50wt! These are the two most commonly used threads, and we are frequently asked to compare them.


The 50wt is wonderful for piecing, subtle quilting & topstitching, and English paper piecing. The slightly thinner weight creates more accurate and flatter seams. Our 50wt is wound on the classic, iconic, orange spool.

It is available in all 270 colors, on a small spool of 220 yards (or 200 meters), a large spool of 1422 yards (or 1300 meters) or a cone of 6452 yards (or 5900 meters). It is best used for English Paper Piecing, Machine Appliqué (Straight Stitch, ZigZag, Blind Hem and Blanket Stitch), Machine Embroidery, and Machine and Longarm Quilting. You should use a 70/10 or 80/12 for your domestic machine (use 50wt in the bobbin) Longarm quilters will use 4.0 Longarm Needles (use 50wt in the bobbin).


40wt thread comes on a green spool. Because of its slightly thicker weight, it is perfect for use with sewing bags, toys or dolls, garments or when you want your topstitching or quilting to show up a little more. Like our previous weights, it is also available in all 270 colors on a small spool of 164 yards (150 meters), a large spool of 1094 yards (1,000 meters) and a cone of 5140 yards (5000 meters).

40wt is recommended for Machine Quilting, Hand Piecing, Bobbin and Machine Lace, Machine Appliqué, Machine Embroidery, and Custom Longarm Quilting. You should use 80/12 needle with 40wt or 50wt in the bobbin. Longarm quilters will use a 3.5 or 4.0 Longarm Quilting Needle (50wt in the bobbin).

Let’s meet again next week to talk about mercerized cotton and long staple before we go over our 80wt, Wool, and Cotton Floss threads


    1. Hi Carol – 50wt is fantastic for paper-piecing! Same needle works great, simply decrease your stitch length as you normally would. Happy Sunday!

  1. I have yet to try your product, and am inclined to do so because of the wonderful explanation in the thread brochure. Thank you! This knowledge is now in my arsenal of tools!

    1. We’re so happy to hear that! Thank you for following along with us:). We’d love to hear what you think!

    2. Do try Aurifil. I never imagined that thread was so important until my first Aurifil spool. Seams lay flatter, less lint gathers in the machine, thread rarely breaks, and thread doesn’t show in seam lines. It’s strong and beautiful and I love sewing with it.

  2. I have often wondered about the *’s on the thread chart, this is great information! I’m loving the series! I am new to using 40 wt.and will definitely give it to my longarmer next time along with 50 wt. for the bobbin.

  3. Love all the information. I never knew about the reactive threads. I was wondering if the * is also on the thread itself? I am definitely interested in getting my hands on a color card.

    1. Hi Kathleen —

      That was a very good question and I had to double check. The * is not on the thread itself. We’re passing new ideas along to our HQ every day, so I’ll pass that one along. In the meantime, we’ll work on new ways to call out the differences so that reactive colors are easy to spot:).

      Have a great day!

  4. Thank you for all the great information, I’ve been a quilter for over 10 years but never knew the importance of a good quality thread. Now I only use Aurifil. I’m enjoying reading all about it, there is just so much I never knew!

    1. Hi Brenda, We are so glad that the series has been helpful and thrilled to hear that you are loving our thread:). Thanks for following along with us!

  5. This is so interesting. Are there specific washing instructions for multicolor thread? I had an issue several months ago with a multicolor thread bleeding on a finished quilt. 🙁 The impact was very slight so if it had been for regular use it would have been fine, but since the quilt will be in a show I was so disappointed!

    1. Hi Sarah —

      First, I’m so sorry to hear that there was an issue with bleeding on a recent quilt of yours. If you’d like to send an email to, we’d be happy to see if there is any way that we can help out!

      Second, great question about the multicolor threads. I’m going to go ahead and add those instructions into the post now! You should see them within about 15 minutes.


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