Nordkalk: Finnish Quality – How to Choose the Right Lime for Your Hens, Horse, or Mortar

If you’ve ever wondered why eggs from one farm have shells that crack firmly on the pan, while from another they crumble in your hand before they even reach the pot, the answer is often as simple as it is surprising: lime. Or, more precisely, its quality and how you use it. Here in the country, there’s one operator that’s been doing this for decades, whether it’s for the cattle shed, the stable, or the construction site – Nordkalk.

In my experience, the biggest problem isn’t that people don’t buy lime, it’s that they don’t always know which product is meant for which purpose. Not to mention the fact that lime isn’t just lime. It’s a raw material with hundreds of different uses, from what goes into an animal’s feed to what gets mixed into mortar when you’re building a new house.

From Finnish stone to the hen's bowl

When you walk down the aisle of an agricultural or hardware store and stop where it says Nordkalk, you know you're looking at a product that’s been quarried and processed right here in Finland, often from the finest Gotland or domestic limestone. It’s pure, with a calcium content around the 36 per cent mark, and most importantly – it has 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 the coarseness. The feed lime is ground to a fineness of about 1–1.5 mm. It dissolves quickly and is therefore ideal for mixed feed for cattle, pigs, and horses, but also for hens if you’re fermenting their food yourself. Hen lime, on the other hand, is a coarser grit, around 3–6 mm in size. It dissolves more slowly, and that’s exactly why it’s the best option for laying hens.

• Feed lime (1 mm): Rapid solubility, suitable for horses, cattle, pigs, and hens when mixed into porridge or wet feed.
• Hen lime (3–6 mm): Slow-release, maintains calcium availability throughout the shell-forming process. Offered in a separate container.
• Grower lime (3 mm): Coarser than feed lime but finer than hen lime. Suitable for growing pullets.

When feeding hens, it’s also worth remembering that a calcium deficiency doesn’t show up overnight. It shows up when one day you notice a hen isn’t moving with the same energy, 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 bag.

Construction lime is no joke

Then let’s go to the other end of the spectrum. When we’re talking about Sammutettu Kalkki Nordkalk Sl 90 30kg, we’re no longer in the hen house – we’re in a completely different world. This is proper construction lime, calcium hydroxide (Ca(OH)2), used for making mortar and lime paint. It’s slaked lime, created when water is added to quicklime – a powerful reaction that releases heat.

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

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

Stones and minerals – so much more than just dust

When we talk about minerals, many people think of jewellery or ore deposits in Lapland. But the reality is much more everyday. Finland has an incredible variety of rock types and minerals – mineral, agate, flint, alabaster, chert – no matter what you call them, they are all part of the bedrock we stand on here.

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 re-use our own by-products and processed aggregates. The University of Oulu is currently running courses on geo-construction and the circular economy, and the Continuous Learning Service Centre Jotpa has invested nearly three million euros in training to develop this very field.

So, it’s not just about sweeping up stone dust from the shed. This is about building the future, where minerals, such as dicopper chloride trihydroxide or even concretion-type iron and manganese deposits, are given a new lease of life. And the best part is, the same principle applies on the farm level: when the eggshell is strong, it’s a sign that the lime cycle is working.

How to choose the right bag?

If you’re standing in front of the shelf in the shop wondering which one is for you, go with this logic:

• For a horse or large cattle: Nordkalk Ruokintakalkki 20kg, mixed into feed or porridge.
• For laying hens: Nordkalk Aito kanakalkki 40 kg, offered freely in its own container or mixed into a home-made feed blend.
• For young pullets and chicks: Grower lime (3 mm), which has enough coarseness but isn’t too slow to dissolve.
• For making mortar, lime paint, or treating sludge: Sammutettu Kalkki Nordkalk SL 90 30kg, but remember your protective gear.

And one final tip: if your hens’ eggshells are starting to thin, you don’t need any fancy products. Get a 20 kg bag of feed lime or hen lime, and you’re sorted. Dose about 100 grams for every kilo of feed, and calcium deficiency shouldn’t be a problem anymore. In my own stable, I’ve noticed that regular Nordkalk feeding also keeps the horses’ hooves in better condition – because calcium isn’t just for eggshells.

It’s a blessing in Finland that we have our own lime industry that understands this country’s soil and the needs of its animals. That shows in every bag. When you buy domestic, you know what you’re getting.