What to Know About Mothproof Wool Fiber

Moths on a wool sweater

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One thing that strikes fear in the hearts of many knitters who like working with natural fibers is the idea that moths could get into their stash and destroy it. It's pretty rare to have a full-on infestation, but such things can happen.

Dealing with Moths in Your Yarn

Let's take a minute to note that if you do have a problem with moths, or have had in the past, it's not a sign that you aren't cleaning enough or that you are disorganized. Moths travel where they can and consume what they can get.

You should also know what you need to do to deal with the problem of moths before you lose your stash. Read this great article from Zen of Making about how she dealt with clothes moths in her Brooklyn apartment without using chemicals. Scary, but important information if you need to know it.

Is Mothproof Wool the Answer?

If you've had an infestation or are worried about one, you might want to choose fibers that are less likely to be damaged by moths. They won't go for manufactured stuff, of course, but if you still love natural fibers, there is an option in mothproof wool.

Many yarn manufacturers make mothproof wool, which is chemically treated to repel or kill moths that come in contact with it. It sounds like a great idea to some knitters, while others are a little nervous at the prospect of having chemicals they don't know much about so close to their skin.

We asked Robert Wells of Brown Sheep Company about the process that is used to mothproof wool. He told us that the chemical used to mothproof wool, Mitin FF, is added to the yarn in the dye bath at the same time as any coloring that is being added to the yarn. The mothproofing agent similarly adheres to the yarn as the dye does.

It means that like dye, the chemical will not rub off or wash off in normal cleaning or dry cleaning.

Mitin FF is a pesticide that works by killing the moth larvae when they ingest and digest the wool protein, which means if you do ever get moths in your stash, they won't be able to do a lot of damage.

But if the chemical kills moths, what can it do to humans? Wells said Mitin FF is relatively harmless if not ingested, and the federal government agrees. Mitin FF has been used as a pesticide in the United States since 1948 and is used exclusively by the textile industry for mothproofing wool. Laboratory tests have found the chemical to be "low to moderately toxic" and to have "low mammalian toxicity."

While there's no danger from using mothproofed wool, some people prefer not to use yarn with extra chemicals. For those people, a whole new world of organic wools and cotton are available, allowing you to create without the chemicals.