Is Cassette Tape Knitting Safe?

Is Cassette Tape Knitting Safe?

We got a great reader question about cassette tape knitting that I’ve been researching. Let’s take a look at how safe it is to craft with the tape part of old cassettes.

We love alternative yarns around here! In fact, I shared a roundup on how to make (and where to buy) eco-friendly yarn just last fall. Conventional wool and acrylic yarns are not great for animals or for the planet. Any alternative to those options seems like a green crafting no-brainer, right? Not so fast.

I want to say up front that my findings about cassette tape knitting were a little bit confusing. There are some good discussions on the topic online, but as far as science it’s not really all in. I tried calling my local extension office and hazardous waste disposal centers, and everyone I spoke to was stumped. Cassette tapes are so outdated that even these folks don’t really deal with them on a regular basis.

Cassette Tape Knitting and Safety

So, what’s the worry with using cassette tapes as yarn sources? This discussion on Flickr sums it up nicely. The problem is something that crafters call “black dust.”

Some crafters who are using cassettes as yarn sources report that the tape sheds little black flakes, and there’s a question about whether it’s safe for that to come in contact with your skin. And what if you inhale those particles? Here’s the down-and-dirty in handy bullet points:

  • Cassette tape is coated with chemicals, which are part of the recording process. Those chemicals include: magnetite, cobalt, and chromium dioxide. The chemicals vary depending on the age of the tape – different companies used different formulations. Not all chemicals are harmful, and we’ll look at the chemicals in cassettes one by one below.
  • Exposure to air causes tape to break down and shed those chemicals. This can happen during the crafting process or while using the finished product.
  • Those chemicals get on your skin and you can inhale them. This can be bad if the chemicals are toxic to humans.

So! How safe are the chemicals in cassette tapes? Let’s look at each one! It’s about to get a little bit sciency up in here.

magnetite (aka iron oxide)

Iron is a chemical that our bodies actually need in small doses. It’s called a trace mineral, which means we need very little to stay healthy. It also means that large doses of iron can be toxic. Is the amount of iron in black dust toxic? I had a hard time finding out how much iron a cassette tape tends to shed, and it varies depending on temperature and moisture.


Cobalt is another trace mineral that can be toxic in large doses. From what I’m seeing, it takes long-term exposure to large amounts of cobalt before you see symptoms of poisoning. That means crafters who use cassette tapes for knitting and crochet on a regular basis might need to be careful here, but knitting the occasional cassette tape beer coozie might be OK.

chromium dioxide

Chromium dioxide seems to be the most worrisome part of a cassette tape. It’s a known lung irritant when you inhale dust or vapors that contain it. From what I’m reading, the vapors are the most toxic, so if you do still want to do some cassette tape knitting, you don’t want to expose your tape to high temperatures. Step away from the hot glue gun, in other words.I would love to hear from crafters out there! Do you craft with old cassette tapes? Have you experienced black dust or any side effects? Let’s share experiences and information in the comments!

Image Credit: Unraveled Tape via Shutterstock

1 thought on “Is Cassette Tape Knitting Safe?”

  1. I’d been looking for this info and i’m glad i finally came across someone who was more successful with the digging.
    But indeed, music cassettes, VHS or data, magnetic tapes seem to be toxic.

    Inhaling iron, cobalt or chromium is not healthy for one’s lungs or the environment.
    Whether while knitting or because the knitted tape will surely degrade, releasing it’s surface much quicker than if you keep listening to them, it will end up in our systems and in water systems.
    It’s probably not easy to clean it out of water either, at least not for facilities in place today. It’s not for antiquity that hazardous waste disposal centres have no answer to this…recovering, for recycling, substances like that is not such a simple and widespread thing as one is lead to believe. I suppose it’s just not profitable anyway.

    Even if the minerals are part of nature and humans, I highly doubt they could be absorbed to be useful, instead of harmful, after how they are processed and combined in tapes.
    I’d probably still wear my 4m long skirt train and effect VHS ribbons for a special evening, though.

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