Nordkalk: Finnish quality – how to choose the right lime for your chooks, horses, or mortar

If you’ve ever wondered why eggshells on one farm hit the pan with a nice, firm crack, while on another they crumble in your hands before they even make it to the pot, the answer is often as simple as it is surprising: lime. Or, to be more precise, its quality and how it’s used. Here in Finland, there’s one company that’s been at it for decades, supplying everything from cow sheds to stables and construction sites – Nordkalk.

In my experience, the biggest issue isn't that people don't buy lime; it’s that they don’t always know which product is meant for which job. Not to mention that lime isn’t just one thing. It’s a raw material with hundreds of different uses, from what you add to animal feed to what you mix into mortar when building a new house.

From Finnish rock to the chook feeder

When you walk into a farm supply store or hardware shop and spot a shelf with Nordkalk on it, you know you're looking at a product that’s been quarried and processed right here in Finland, often from the best possible Gotland or domestic limestone. It’s pure, with a calcium content sitting around 36 per cent, and importantly – no unnecessary additives. Animals need calcium for the same reasons we do: for bone development, nervous system function, and heart rhythm.

But what's the difference between, say, a bag of Nordkalk Ruokintakalkki 20kg and Nordkalk Aito kanakalkki 40 kg? It's simply about particle size. The feed lime is ground to a fineness of about 1–1.5 mm. It dissolves quickly, making it ideal for mixed rations for cattle, pigs, and horses, but also for chickens if you're fermenting their feed yourself. Chicken lime, on the other hand, is a coarser grit, around 3–6 mm. It dissolves more slowly, which is precisely why it's the best option for laying hens.

• Feed lime (1 mm): Fast dissolving, suitable for horses, cattle, pigs, and chickens when mixed into mash or wet feed.
• Chicken lime (3–6 mm): Slow-release, helps maintain calcium levels throughout the shell-forming process. Offer it free-choice in a separate container.
• Grower lime (3 mm): Coarser than feed lime but finer than chicken lime. Suitable for growing pullets.

When feeding chickens, remember that a calcium deficiency won't show up overnight. It shows up when one day you notice the birds aren’t moving with the same energy, and the eggshells feel thinner. I’ve seen farms switch back to Nordkalk products simply because the quality of the feed lime is so consistent. The grind is spot on, and there are no stones or impurities in the bag.

Construction lime is serious stuff

Now, let’s look at the other end of the spectrum. When we talk about Sammutettu Kalkki Nordkalk Sl 90 30kg, we’re no longer in the chook shed – we’re in a completely different world. This is proper construction lime, calcium hydroxide (Ca(OH)2), used for making mortar and limewash. It’s hydrated lime, created by adding water to quicklime – a process that triggers a strong reaction and releases heat.

You don’t want to mess around with this product. As the label warns, it irritates skin and eyes and can cause respiratory irritation. But when used correctly, it’s invaluable. It’s also used for stabilising septic tank sludge. If you've ever wondered why old houses have such healthy indoor air, one reason is the lime mortar, which breathes and absorbs impurities.

Nordkalk SL 90 is often made from Gotland limestone, but it’s processed in Finland. It’s ground and hydrated to just the right consistency to create a strong, long-lasting mortar. For builders, it’s a reliable choice when you want traditional durability.

Rocks and minerals – more than just dust

When people talk about minerals, many think of jewellery or ore deposits up north. But the reality is much more down-to-earth. Finland has an incredible variety of rock types and minerals – mineraali, agate, flint, alabaster, chert – whatever you call them, they’re all part of the bedrock we stand on.

What’s interesting is that we’re starting to understand the importance of recycling these materials. In the mining industry, there’s a lot of talk about conflict minerals, but here in Finland, the focus is shifting to how we can reuse our own by-products and processed aggregates. The University of Oulu is currently running courses on geoconstruction and the circular economy, and the Jotpa Centre for Continuous Learning has invested nearly three million euros in training to develop this very field.

So, it’s not just about sweeping up rock dust from the barn. This is about building the future, where minerals like dicopper chloride trihydroxide or concretion-type iron and manganese deposits are given a new lease on life. And the best part? The same principle applies on the farm: when the eggshells are strong, it’s a sign the lime cycle is working.

How to choose the right bag?

If you’re standing in front of the shelf wondering which product is the one for you, follow this logic:

• For horses or large cattle: Nordkalk Ruokintakalkki 20kg, mixed into the feed or mash.
• For laying hens: Nordkalk Aito kanakalkki 40 kg, offered free-choice in a separate container or mixed into a homemade feed blend.
• For young pullets and chicks: Grower lime (3 mm), with enough coarseness but not too slow a release rate.
• For making mortar, limewash, or sludge treatment: Sammutettu Kalkki Nordkalk SL 90 30kg, but remember to use your protective gear.

And one final tip: if your chickens' eggshells have started to thin, you don’t need any fancy additives. Grab a 20 kg bag of feed lime or chicken lime, and you’re sorted. Use about 100 grams for every kilo of feed, and calcium deficiency shouldn't be an issue. In my own stable, I’ve noticed that regular Nordkalk supplementation even keeps the horses’ hooves in better condition – because calcium isn’t just for eggshells.

We’re lucky in Finland to have our own lime industry that understands our local geology and the needs of our animals. You can see it in every bag. When you buy local, you know what you’re getting.