roasters corner-feb


Cast your minds back if you will to 2012. It was the year that the Queen celebrated 60 years on the throne, the UK basked in the reflected glory of its Olympic and Paralympic athletes and the US re-elected Barack Obama as president. In the coffee world, there was a consensus that water could influence the character and flavour of a cup of coffee, but the general view was that hard water was bad, soft water was good.

Carvetii coffee was very much in its infancy, having been established in the latter part of 2011, and like many new business owners, we were on a steep learning curve!

We already had some good local support, and our coffee was making its mark on a region traditionally served by roasts with a much darker product. In between production and chasing new sales we were scouring every possible information source on coffee to make sure we had the best possible understanding of our product.

At this time, we had the opportunity to supply a pop-up cafe in London. The prospect of this account was exciting in that it promised some decent sales volume over a three-month period, and it also allowed us to showcase our coffee in one of the cities at the forefront of the growing third wave coffee movement. One of those involved in the pop-up had been enjoying our coffee locally and was keen to use it in this venture.

All began well and our coffee performed as expected and was well received by customers. Partway through the relationship, we changed the components in our espresso blend, which we do every three or four months to use seasonally fresh coffees.

Then the troubles began! We received a phone call from the café concerned and discovered that the coffee tasted over-roasted and smoky. This was news to us as we regularly taste batches of coffee each week. We apologised, re-roasted a batch, tasted the coffee to make sure all was well and shipped it to the customer. No harm was done and the customer was pleased with our quick and positive response.

Imagine our horror when we received another phone call with the same complaint. Over roasted and smoky tones to the coffee! How could this be? They were using the same make of espresso machine and grinder as us (we actually supplied the kit), they were following the same recipe and, as we knew London water was very hard, we had fitted an appropriate water filter.

Then it dawned on us – water was the only difference between the two sites, and while the water in London had been filtered to remove minerals, we had not taken a close look at the water in our Roastery. We knew it was very soft but the commonly held view was that soft water had little impact on coffee while hard water did.

Our next stop was the local supermarket and a trawl of the shelves to find bottled water that would mimic the water in London. Evian was a great candidate in this respect with a dry residue of 345mg/l (compare that to Volvic, which is widely regarded as being good water for coffee, at 130mg/l). The dry residue refers to the amount of dissolved solids in the water.

We returned to the Roastery and sampled our espresso blend on the two different waters – Evian and our tap water (which was fitted with a carbon filter to reduce odours and flavour taints, though only gave a dissolved solid reading of 4.8ppm). Much to our surprise, the difference in the flavour and character of the two coffees was remarkable!

The espresso made using local water was bright and fruity as a result of the components we selected and the contemporary roast style. The espresso made with Evian tasted very different – the acidity was muted and there was a definite ‘roasted’ tone to the coffee.

 At this point, I think I need to explain the term ‘roasted’, as I see it. There is a flavour we associate with coffee which is present in coffee cake, coffee chocolates and other coffee flavoured products. It is also the flavour we associate with darker roasted coffee offerings on the high street. Given that coffee beans from different origins have the potential to have different flavours, it is the duration spent in the roaster which creates this overall coffee flavour.

Contemporary roast style attempts to harness the origin flavour and character without letting the roast itself dominate the flavour profile. If you buy a piece of salt-marsh lamb you want to cook it carefully and lightly, so those herby tones come through on the plate. Leave it in the oven for a long time and it will end up tasting just like, well, lamb!

So, to discover that our coffee tasted ‘roasted’ was somewhat devastating for a roaster who was pitching themselves firmly into the contemporary and speciality market. We had to do something but the challenge was to understand the cause when much of the coffee world still saw soft water in a positive light.

It is worth noting that our water at the Roastery is very soft – 4.8ppm is about as low as it gets! This is due to the hard nature of the rocks in our region – rain falls from the sky, quickly carries over the hard mountains and collects in lakes and reservoirs, which are again located on hard rocks.

There is no opportunity for the water to dissolve minerals on its route to our taps. Contrast that with London water which comes from aquifers in the ground – the water will have passed through soft, chalky rocks and on its journey will have become very mineralised.

Our solution in the short term was to quality control our coffee on two types of water, that which came from the tap and then Evian. If the coffee held up on both waters, then we knew it could be sold with confidence. If not, it was back to the drawing board and a new roast profile.

This was not a long-term solution – I hate not knowing why and at the time there was very little material around which supported our theory that soft water was not necessarily a good thing. In addition, it is nigh on impossible to run a full-sized espresso machine on Evian bottled water! I needed a way to remineralise our local water, so we could effectively have mineralised water on tap!

Today our knowledge about water and its influence on coffee is very different. Following on from the 2015 publication of Water for Coffee by Christopher H. Hendon and Maxwell Colonna-Dashwood, we now know that there is a ‘perfect’ water quality for coffee and that both very soft and very hard waters can have a negative impact on the cup. Water filtration has leapt forwards and it is now possible to buy water jugs with adaptable filters, allowing you to tailor the water you use at home.

At our Roastery we are able to remineralise our local tap water in bulk, making it the perfect water for coffee, and we quality-control our roasting against this. We are able to run our espresso machines and filter brewers on this water, but we also check our coffee on the soft, local water which is the only water many of our customers have access to.

From a coffee roasting perspective, what we do know is this:

If you live in a soft water area, and only taste your coffee on soft water, it is very possible that your coffee will taste very different in hard water areas. If you are aiming for a light, contemporary roast your coffee could taste darker than you anticipated, and if you are aiming for a dark roast then harder water can make your coffee taste even darker!

Conversely, if you live in a hard water area and only taste your coffee on hard water, you are going to experience similar issues. A light roast will taste even lighter in soft water, and often the acidity associated with light roasts will become sour and overpowering. Dark roasts can often taste lighter on soft water, so this is perhaps less of a problem.

If you quality control your coffee on perfect coffee brewing water, it is likely that it will hold its own on all waters.

I often think that this issue with water came at the perfect time for our business. The challenge of understanding the problem and finding a solution resulted in a leap in understanding both the water and roasting front. Over the past 9 years, we have adapted and evolved our coffee roasting as our knowledge has developed. However, the gains we made as a result of water probably had the biggest single impact on our coffee.

In the next article, I am going to look at water in a little more depth though from the perspective of a non-scientific mind! I’ll share the solution we arrived at and take a look at some of the options you can try if you want to improve the water you use to brew coffee.

Gareth Kimble is the founder and co owner of Carvetii Coffee


  1. OMG! You just made me realize that filtered water can influence the after-taste of coffee as well. My husband is a coffee lover (not as much as he loves me, thankfully) and I want to prepare something special for him next week. I’ll remember this tip when I make a purchase later.

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