April 4, 2009

100% merino wool interlock fabric

I thought since I didn't find much information about this on the web, that I would do my own experimentation and post it here on the blog.

I received my 100% merino wool interlock in the mail a few days ago, but have been tossing and turning at night thinking about how to best felt it, without ruining the $20 /yard fabric. I have read that you are just supposed to wash it on hot a few times and it will take care of itself, but it just seemed to be the opposite of what I have learned all of these years about wool, that I couldn't get myself to through the whole 2 yards into the washer and just hope!

Just a few things beforehand: I have a German front-loading washer. It has temperature settings, and heats the water with a heating element. So the cold water goes in and is slowly heated up to the desired temperature. I wasn't sure what to call a warm or hot cycle, so I just picked 40° C (104° F) as a warm cycle and 60° C (140° F) as a hot cycle. My washer also only has a cold water rinse, so the wool is always going to be shocked after warming up.

So, I decided I would try small swatches first, to see what the results would be. I cut three pieces of the fabric, each 3 1/2" wide by 4 1/2" long. First, I threw a piece in with my shower curtain on a warm cycle (104° F). I used normal detergent and a cold water rinse. It didn't look like it had changed very much, so I just left it and didn't put it in the dryer. I think one of the reasons why it didn't get much smaller, is because the swatch got hung up on the glass of the front loader and didn't get as much agitation as it would if it had stayed in the drum of the machine. The result wasn't much thicker that the original. This is what it looked like compared to the original unwashed swatch on the left:

This is the results of the same swatch (on the left in the above picture) being washed again on a warm cycle (40° C). I can't see much difference, really... but again the thing to hung up and didn't agitate much at all.

Next , I threw one unwashed swatch in with my normal diaper wash at a temperature of 60° C (140° F). The result is much smaller and thicker than the swatch that I had at the warm temperature wash.

Then I threw it in the hot dryer for about 40 minutes or so. I don't think it changed much in size or thickness - maybe a bit fluffier and softer. This is what came out:

Now just to see how much further the "hot-cycle" swatch would shrink/felt, I put it into a second hot water wash cycle. Results (not much difference - maybe a tad bit smaller):

And finally same "hot-cycle" swatch, after 40 minutes in the hot dryer:

So in conclusion, though I have not attempted to felt all of the fabric yet, I think that one hot water wash would be fine for the 100% wool interlock fabric to make diaper covers. You could even venture a second hot wash, without over felting.

After felting 100% merino wool interlock, I would not attempt to wash the finished product (diaper cover) in the regular wash... I would still recommend hand wash with a homemade wool wash and lanolin.


  1. Can't wait to see what the finished product looks like! Are you leaving it natural or dyeing it?

  2. I had no idea you could such a thing! Truly wonderful! Thanks for putting this on the web!!!

  3. Great post! Very informative.

  4. I'm a cloth diapering mom and I have been looking for the same kind of fabric for wool diaper covers! Where did you get it? Are you still pretty pleased with it after using it for a while? Wow, you have a great post & pictures about your felting experiment! Thanks for all the info!

  5. where do you buy the wool interlock? thanks for experimenting for us!

  6. Where can I find wool interlock??? Where did you find yours???