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Channelling in coffee occurs during the extraction process when water finds a gap in the coffee puck. This means that the water that would typically apply even pressure to the puck and extract flavours makes a beeline to the gap (because water always chooses the path of least resistance) and causes a weak shot with no flavour. A channelled shot is easy to miss when you don’t know what you’re looking for and even baristas have been known not to realise that they’ve done it. In our cafe, we have a rule that if you channel, you have to do ten push-ups. It’s a great way to avoid channelling, as it makes you focus on ensuring every step is done correctly!
How to spot it
A way to spot it is by looking at how it pours, a weak, watery, thin pour with little to no crema is a sign that the shot has channelled.
Common Causes & How To Avoid It
Warning; you’re about to hear the word “even” and “level” a lot because that really is what avoiding channelling is all about – making sure your grind and tamp is even and level so that the water that applies the pressure that extracts the coffee has no reason to only target one part/side of the coffee puck. There are a few causes for why the puck may be uneven or not level, so we’ve listed some common reasons below!
If you’ve ground your coffee and notice that the grinds are uneven, meaning there are really fine grinds mixed with larger grinds and maybe even chopped beans that haven’t even been ground at all, don’t make a shot out of it! It will make it impossible to create an even, consistent coffee surface for the water to apply pressure to evenly. It will also prevent the coffee grinds from interlocking with each other, which creates a barrier for the water to resist against. To find out more on why investing in a grinder is so important to your home coffee set up, check out our other blog post here!
Not Enough Coffee
Not having enough coffee grinds in your basket may lead to channelling, even if you get the surface even and grind consistency correct. This is because there’s not enough coffee to resist against the water. A general tip is to have 2g more of coffee in your basket than the basket size. For example, if you have a 22g basket, you’ll want to grind 23-24g of coffee.
A wet basket
Make sure your basket is dry as a wet basket will lead the water that is applying pressure to gravitate to edge of the basket and not apply evenly through it.
Avoid an uneven tamp by making sure the coffee distributes evenly in the basket when it’s being ground by wiggling the portafilter. Then when tamping, make sure you’re applying a level, even amount of pressure. Too much pressure to one side of the basket will cause the water to go for the weaker side.
A tool that will help with uneven surfaces is a distribution tool like this one here from ONA Coffee.
A tool like this aims to make it easier to create a perfectly even, level surface to tamp, which will reduce your chances of channelling.
Tapping the side of your portafilter
Tapping the side of your portafilter is an old technique that is still being used today with the idea that it evens out the coffee grinds. It’s problematic though because if you look closely, it causes the grinds to break away from the edge of the basket, creating a tiny gap which the water will travel to. Check out a full blog on why you should never tap the side of your portafilter here!
To recap, the main thing to remember when avoiding channelling is to make sure that your prep stages (grinding the coffee and tamping) are done evenly and level. Take into account other factors as well such as making sure you have the right amount of grinds for your basket size, that your portafilter is not wet and that you aren’t tapping the side of your portafilter. If you remember this, you’ll absolutely reduce the number of times you’re channelling, or even better, stop you from getting channelled shots completely!