Are you ready?

Are you ready for the extreme geekness that’s about to come down upon you? Grip yourself, sit down, and maybe get your eyes ready to roll.

When I washed the body of the Adrienne Vittadini sweater, the yarn bled like a mofo. It was not pretty. Bloggers chimed in and suggested a variety of remedies: Synthrapol, vinegar, even microwaving! It was time to put these suggestions to the test.

Background and significance: I knew the KFI Cashmereno used for knitting my grandma’s Best Foot Forward socks would bleed. How did I know that? It turned my fingers blue after knitting for long periods of time. I was pretty resolved to figure out how to stop yarn from bleeding, so it was time to do some experiments.


  • basin, running hot and cold water
  • Tide
  • Synthrapol
  • vinegar
  • 1 pair of grandma’s Best Foot Forward Socks

Experiment 1: Synthrapol. The description of this product is really vague: it’s not immediately clear to me whether it’s supposed to help all the excess dye leave the fabric, or whether it’s supposed to trap all the excess dye particles and permanently set them in the yarn.

Hypothesis 1: Synthrapol traps excess dye particles and deposits them inside the yarn.

Methods: I filled the basin with lukewarm water, and added a capful of Synthrapol as well as some Tide. I placed the socks into the mixture.


The socks bled like mofos. Synthrapol does not attach excess dye particles to the fabric.

Hypothesis 2: Synthrapol helps excess dye leave the fabric. Since the socks have already been treated with Synthrapol once and lost a lot of dye in the process, perhaps Synthrapol released all the excess dye into the water already, and no more bleeding would occur. If this is the case, then placing the socks into fresh water will no longer turn the water blue.

Methods: Place socks into a fresh batch of lukewarm water and Synthrapol.

Results: The socks bled like mofos (data not shown). Synthrapol does not eliminate all the excess dye after one wash, since the socks continue to bleed.

Experiment 2: vinegar. It looked like the socks had a lot more blue dye to lose after two Synthrapol washes, so I had enough material for a second experiment.

Hypothesis: Vinegar traps excess dye particles and deposits them inside the yarn.

Methods: I filled the basin with lukewarm water, added a bit of vinegar, then added the socks.


Considering how much excess blue dye I expected after the second Synthrapol wash, I think the vinegar actually helped to trap the dye and deposit it inside the yarn! The water was just barely blue.

Follow-up experiment: Since I didn’t want grandmother’s sock to smell like vinegar, nor did I want them to spontaneously start releasing excess blue dye every time the pair wasn’t washed in vinegar, I insisted on following the vinegar wash with a traditional water & detergent wash.

Hypothesis: The vinegar traps excess dye permanently, so the dye never bleeds again.

Methods: I filled the basin with a fresh batch of lukewarm water, added a drop of Tide, then submerged the socks.


The hypothesis was correct! Following the vinegar wash with a traditional detergent & water wash didn’t counteract or reverse the setting/trapping effects of the vinegar. The water was almost unnoticeably blue.

Conclusions: I am not sure what the Synthrapol does. It neither allowed all the dye to leave the fabric at once, since the yarn bled after the 1st wash, nor did it permanently set the excess dye particles inside the fabric. Foo on you, Synthrapol! Vinegar, a cheap and common consumable, seems to attach the excess dye particles to the knit fabric, since it stops dye bleeding when it’s expected. This effect is permanent: a common soap and water washing does not reverse it. In the future it would be useful to test the vinegar on bleeding fabric that hadn’t been washed twice in Synthrapol.


25 thoughts on “Are you ready?

  1. Judy

    Well hypothesized! Also very useful to know. Waiting to see the next set of experiments with non-synthrapoled fabric. 😉

  2. Janice in GA

    A quick bit of Googling seems to indicate that synthrapol is good for removing *fiber reactive* dyes (i.e., dyes generally used on plant fibers.) (See for one.) It’s also good for washing fabric/fiber BEFORE dyeing too.

    Lots of dyeing methods (Kool-Aid dyeing is a frequent example) use vinegar to lower the pH of the dye solution so that the dye reaction can take place. So seeing the vinegar set the dye on your wool socks makes sense.

  3. jody

    Great post. Thanks for sharing the details — and showing us that the cheap ‘n easy can really be a good thing!

  4. Laurie

    I’m glad you followed the vinegar wash with a Tide wash. If my socks smelled like vinegar I’d wander around all day and not know why I craved a salad!

    Good job on the testing. I’m sure Grandma’s feet thank you.

  5. jess

    Ah! good to know: I picked up some of the dark navy kfi cashmereno for socks for a friend a couple of weeks ago, so I bet I will encounter the same thing (however my kfi cashmereno socks didn’t bleed at all in the burgundy and mint green colors… interesting).

  6. claudia

    Well, to my knowledge (granted, which is not exhaustive), vinegar only sets the dye on the yarn at temperature — a simmer and for 20 minutes at that. I’ve never heard of vinegar doing anything at a lukewarm temperature.

    I guess the one untested hypothesis is whether two washings in Synthrapol remove all excess dye, leaving nothing left for a third bath of whatever composition.

  7. mamacate

    I haven’t done cotton dyeing since I was a kid, but my understanding is that for wool, sythrapol is just a wetting agent–to help the water really penetrate the fibers (thereby allowing the dye to do the same). You can substitute dish soap for acid/protein dyeing. The vinegar would be a mordant, so it would help the exhausting dye bond with the fibers, just like in the original dyebath. You might find the DyersList (it’s hosted by a university listserv, not yahoo–google it) interesting–there is a lot of discussion there of the chemical processes involved in dyeing. Most of it is over my head, but it’s interesting to lurk. PS thanks for the info on bryspun circs.

  8. Barb

    I don’t know why I didn’t think of mentioning this to you before, because this is right up your alley:

    From Fiber to Fabric: The Essential Guide to Quiltmaking Textiles by Harriet Hargrave is, yes, about fabrics, but get this out of the library and check out the experiments she does to check color-fastness, etc. I took a class with her and she has a scientific background–if I remember correctly, she even tests Synthrapol and will tell you exactly what it is supposed to do!

  9. paula

    When I saw that vinegar, I knew it would somehow come through! I received a nifty little book years ago packed with all sorts of uses for vinegar. It’s extremely versatile for cleaning, disinfecting and all kinds of other things. The ENTIRE book was filled with these tidbits.

    Thank god you washed those socks. Can you imagine if poor Grandma put those in with her unmentionables?

    That would not have been good. 😉

  10. Colleen

    Wow, are you a scientist or what?

    Thank you for debunking the myth of Synthrapol!

    Just a question (because I read Janice’s comment up there): do you know what type of dye was used for the yarn?

  11. anne

    love your tests!

    when dying cotton fabrics, I use both synthrapol (to wash the fabric before dying, supposedly to get anything out of the fabric that could get in the way of the dye) and ReTayne, which is supposed to remove any excess dye so the fabric won’t bleed. It works for me, using fiber-reactive dyes from Dharma.

    Also try the dye-trapping sheets from your supermarket detergent aisle — woolite makes one — they look like fabric softener sheets, you throw them in the wash, they soak up excess dyes. Quilters swear by them. They work for me.

  12. June

    Yo Dr. K,

    Ever visit the site? From there:

    Synthrapol SP: A concentrated liquid wetting agent and surfactant compatible with all dye classifications. Use with PRO Dye Activator to scour fabric before dyeing. Also recommended for the final hot wash of Reactive Dyes.

    May also be added to the dye bath to add levelness and aid in wetting out the fiber.

    They also have a low-foam variety. I typically use dish detergent as a pre-soak wetting (reduces surface tension), tho I may have a bottle of Synth stashed somewhere. I’ve been told – haven’t tried it myself – that Synthrapol is supposed to help suspend dye particles in the wash water such that it won’t deposit back onto the item. This is supposedly useful when washing fabric with, say, dark blue flowers on a pale yellow background, or a sweater with red and white stripes. Any dye that comes out will just go down the drain instead of leaving irregular stains on the background. The reason I haven’t tried that theory yet is because I always make sure my dyes have truly exhausted with lots of heat and acid before I take it out of the dyepot. (Btw, I prefer citrate over vinegar – the only smell is that of wet, hot wool.)

    I’m inclined to agree – mostly – with Claudia on your test results. However, my own experience (and I think I read it on Elaine Benfatto’s blog, at some point, too) indicates that if you have *really* acidic water, dyes can strike fairly well without heat. At the same time, I don’t know how well it will fix w/o heat. By the 4th wash in anything, the excess dye would have come out of most tiny things like socks.

    While I’m rambling, I believe some Brown Sheep yarns (all? been years since I knit with them) have something about washing in water with a glug vinegar on the label. I don’t recall having a bleeding dye problem with them, so who knows.

    Oy, this comment gets longer and longer. I did some emergency dye-fixing a while ago:

    Grandma’s gonna love her socks.

  13. Christie

    Do I hear Science Project Winner? I think I do!

    Thanks for the FYI…I”m better informed. You get the gold star and the blue ribbon!

  14. Emily

    Comments from Reviewer #1:

    While the author addressed an important question in the field, the experiments lacked sufficient controls to be conclusive. I recommend that the author completes the following experiments before this is published:

    1. Determine whether vinegar works to set the dye without pretreatment with synthrapol.

    2. Determine whether treatment with synthrapol, followed by washing was sufficient to prevent further bleeding of the dye

    Because the results of these experiments are widely applicable and of interest to a large group of people, I recommend that this work be published following the above revisitons.

    (Sorry. I couldn’t help continuing the science reference. Nice info. Hopefully the vinegar works on the sweater too.)

  15. Stephanie

    In my dyeing class last week we used vinegar after the indigo dyeing to set the color. It would seem that if it works for that kind of project, it’s a good choice for commercially dyed yarn as well. Thanks for the tip. I do so love your experiments!

  16. Laura Neal

    My MIL swears that using hair shampoo on your wools will clean them and not have the color run and run. I have yet to try it out. I just buy the stuff that you wash it and then never rinse it. I found mine at a woolen mill. It is Australian, I think.

  17. Margot

    You are my shero, Grumperina. I just made myself a pair of socks [second pair ever, first for me!] that turned my fingers blue as I knit! I was about to experiment with vinegar to set the color but decided to google it first.

    Thanks for taking the experimenting out of my experiment.

  18. Tawny

    Remember Synthrapol is most effective when using as a final hot wash, it is not as effective in luke warm water. I have used this product extensively and ran into the same problem as you in the beginning and was displeased with my results. However when I started using this product in only hot water it works amazingly!


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