You've run out of yarn halfway through a project, ordered another ball in exactly the same colour and… something doesn't look quite right.
It's definitely the same yarn. The shade name and number are the same. But when you put the two balls next to each other, one looks ever so slightly lighter, darker or just different.
Have you been sent the wrong colour?
Most likely, no! The answer could be something called a dye lot.
What is a dye lot?
Yarn isn't all dyed at once. Instead, it's produced and dyed in batches, and each of those batches is given its own dye lot number.
Manufacturers work hard to keep colours consistent, but just like with any dyeing process, there can be tiny variations between batches.
One batch of your favourite pink might be ever so slightly warmer than another. A cream could be a touch lighter. A blue might have a slightly different tone.
On their own, you'd probably look at both and say they're the same colour.
Put them directly next to each other in the same project, though, and that small difference can suddenly become much more noticeable.
Where do I find the dye lot?
Have a look at the label wrapped around your ball of yarn.
Alongside the yarn name and colour or shade number, you should find a dye lot number.
If you're using multiple balls for the same project, ideally you want this number to be the same on all of them.
The shade number tells you which colour you've bought. The dye lot tells you which batch that particular ball came from.
So two balls can have exactly the same shade number but different dye lot numbers.
Why does the dye lot matter?
For some projects, it might not matter at all.
If you're making separate items, using lots of different colours or working on something where the balls won't sit directly alongside one another, a tiny difference may never even be noticeable.
But if you're making something using several balls of the same colour — particularly a jumper, cardigan, blanket or another larger project — it's worth paying attention to those little numbers on the label.
Imagine getting almost to the end of a jumper, starting a new ball and discovering the final section is a slightly different shade!
That's why checking your dye lots before you start can save you a lot of frustration later.
Buy enough for your project at the same time
Where possible, we'd always recommend buying enough yarn to complete your project in one go.
If you buy three balls today and realise a few weeks or months later that you actually needed four, we may have received a new delivery in the meantime.
The yarn will still be the same brand, type and shade, but the new stock could have a different dye lot.
Unfortunately, we can't guarantee that we'll still have a particular dye lot available when you come back for more.
It's always worth checking your pattern, working out how much yarn you're likely to need and adding a little extra if you're unsure.
What if I need another ball?
Don't panic!
If you've already started a project and realise you need more yarn, check the ball band from the yarn you're currently using and find the dye lot number.
You can then get in touch with us before ordering and let us know the yarn, shade and dye lot you're looking for.
If we still have that dye lot available, we can have a look for you.
If we don't, you can still use another dye lot, but you'll need to be aware that there may be a slight colour difference.
And this is another very good reason not to throw those labels away until your project is finished!
Same yarn, same shade, slightly different colour
So, if you've bought your favourite yarn again and you're convinced it looks slightly different from the last ball you had, you might not be imagining it.
Check the labels.
If the shade numbers match but the dye lot numbers are different, you've probably found your answer.
It's a completely normal part of the yarn dyeing process and doesn't mean you've received the wrong yarn — but it's definitely something worth knowing before starting your next big knitting or crochet project.
So next time you're choosing several balls of yarn, have a quick look at those little numbers on the label. Your future self might thank you!