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

If you've ever wondered why eggshells from one farm hit the pan with a solid thud, while on another they crumble in your hand before they even reach the saucepan, the answer is often as simple as it is surprising: lime. Or, more precisely, its quality and how it's used. You see, there’s one name in this country that has been supplying barns, stables and building sites for decades – Nordkalk.

From my own experience, the biggest issue isn't that people don't buy lime, but that they don't always know which product is intended for which purpose. And that’s not to mention the fact that lime isn't just lime. 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 bedrock to the chicken's bowl

When you walk into an agricultural or hardware store and find yourself in the aisle marked Nordkalk, you know you're looking at a product that has been quarried and processed right here in Finland, often from the finest Gotlandic or domestic limestone. It's pure, with a calcium content around 36 per cent, and most importantly – no unnecessary additives. Animals need calcium for the same reasons we do: to develop strong bones, for nervous system function and for heart rhythm.

But what’s the difference between, say, a sack of Nordkalk Feed Lime 20kg and Nordkalk Aito hen lime 40 kg? Simply put, it's the coarseness. Feed lime is ground down to about 1–1.5mm. It dissolves quickly, making it well-suited for mixed feeds for cattle, pigs and horses, but also for chickens if you're fermenting their food yourself. Hen lime, on the other hand, is coarser grit, around 3–6mm. 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 hens when mixed into mash or wet feed.
• Hen Lime (3–6 mm): Slow-dissolving, maintains calcium availability throughout the shell-forming period. To be offered in a separate container.
• Grower Lime (3 mm): Coarser than feed lime, but finer than hen lime. Suitable for growing pullets.

When it comes to feeding hens, it's also worth remembering that a calcium deficiency doesn't show itself immediately. It becomes apparent when you notice, one day, that a hen isn't moving with its usual vigour, and the eggshell feels thinner. I’ve seen farms switch back to Nordkalk products simply because the quality of the feed lime is so consistent. The fineness is spot on, and there are no stones or impurities in the sack.

Construction lime is no joke

Now let's jump to the opposite end of the scale. When we talk about Slaked Lime Nordkalk Sl 90 30kg, we're no longer in the henhouse; we're in a completely different league. This is proper construction lime, calcium hydroxide (Ca(OH)2), used for making mortar and lime paint. It's slaked lime, produced when water is added to quicklime – a vigorous reaction that releases heat.

This is not a product to be messed with. As the product information warns, it irritates skin and eyes and can cause respiratory irritation. But when used correctly, it is 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 precisely the lime mortar, which breathes and binds impurities.

Nordkalk SL 90 is often made from Gotlandic limestone as a raw material, but it is processed in Finland. It's ground and slaked to just the right consistency to make a strong, long-lasting mortar. For builders, it's a reliable choice when you want traditional durability.

Stones and minerals – so much more than just dust

When minerals are mentioned, many people think of jewellery or ore deposits in Lapland. But the reality is far more everyday. Finland has an incredible variety of different rock types and minerals – mineral, 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 now beginning to understand the importance of recycling these stones. In the mining industry, there’s increasing talk about conflict minerals, but in Finland the focus has shifted to how we can reuse our own waste rock and processed aggregates. The University of Oulu is currently running courses on geotechnical construction and the circular economy, and the Continuous Learning Service Centre, Jotpa, has invested nearly three million euros in training to develop this very area.

So it's not just about sweeping up stone dust in 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 of life. And best of all, the same principle applies at farm level: when the eggshell is sound, it's a sign that the calcium cycle is working.

How to choose the right sack?

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

• For horses or large cattle: Nordkalk Feed Lime 20kg, mixed into the feed or mash.
• For laying hens: Nordkalk Aito hen lime 40 kg, offered ad libitum in a separate container or mixed into a homemade feed mix.
• For young growers and chicks: Grower lime (3 mm), coarse enough but not too slow-dissolving.
• For making mortar, lime paint or treating slurry: Slaked Lime Nordkalk SL 90 30kg, but remember your protective gear.

And one final tip: if your hens' eggshells have started to thin, you don't need any fancy supplements. Get a 20kg sack of feed lime or hen lime, and you'll be sorted. Dose about 100 grams per kilogram of feed, and calcium deficiency should no longer be a problem. In my own stable, I've noticed that regular Nordkalk feeding also keeps horses' hooves in better condition – after all, calcium isn't just for eggshells.

We're fortunate in Finland to have our own lime industry that understands the soil of this country and the needs of its animals. It shows in every single sack. When you buy domestic, you know what you're getting.