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

If you've ever wondered why eggshells from one farm give a satisfying crack on the pan while from another they crumble in your hands 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. In this country, there's one player that's been doing this for decades, whether it's for the barn, the stable, or the building site – Nordkalk.

In my experience, the biggest issue isn't whether people buy lime, but that they don't always know which product is meant for which purpose. Not to mention that lime isn't just lime. It's a raw material with hundreds of different uses, from what you put in an animal's feed to what you mix into mortar when building a new house.

From Finnish stone to the chicken's bowl

When you walk down the aisle of a farm supply or hardware store and come to the spot marked Nordkalk, you know you're looking at a product that has 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 most importantly – no unnecessary additives. Animals need calcium for the same reason humans do: for bone development, nervous system function, and heart rhythm.

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

• Feed Lime (1 mm): Fast solubility, suitable for horses, cattle, pigs, and chickens when mixed into mash or wet feed.
• Poultry Lime (3–6 mm): Slow-release, helps maintain calcium availability throughout the shell-forming process. Offered in a separate feeder.
• Grower Lime (3 mm): Coarser than feed lime but finer than poultry lime. Suitable for growing pullets.

When feeding chickens, 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 grind size is spot on, and the bag contains no stones or impurities.

Building lime is no joke

Now let's go to the other end of the spectrum. When we talk about Hydrated Lime Nordkalk Sl 90 30kg, we're no longer in the chook shed; we're in a completely different world. This is proper building lime, calcium hydroxide (Ca(OH)₂), used for making mortar and lime paint. It's hydrated lime, created when water is added to quicklime – a process that produces a strong reaction and releases heat.

This is not a product to mess around 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 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 hydrated to just the right condition to make a strong, long-lasting mortar. For builders, it's a reliable choice when you want traditional durability.

Rocks and minerals – so much more than just dust

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

What's interesting is that we're starting to understand the importance of recycling these stones. In the mining industry, there's more and more talk about conflict minerals, but in Finland, the focus has shifted to how we re-use our own waste rock and processed aggregates. The University of Oulu is currently running courses on geoconstruction and the circular economy, and the Continuous Learning Service Centre Jotpa has invested nearly three million euros in training to develop exactly this area.

So it's not just about sweeping up rock dust from the barn. This is about building for the future, where minerals like dicopper chloride trihydroxide or even concretion-type iron and manganese deposits are given a new life. And best of all, the same principle applies at the farm level: when an 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 wondering which product is right for you, follow this logic:

• For horses or large cattle: Nordkalk Feed Lime 20kg, mixed into feed or mash.
• For laying hens: Nordkalk Aito kanakalkki 40 kg, offered free-choice in a separate container or mixed into homemade feed blends.
• For young pullets and chicks: Grower Lime (3 mm), coarse enough but not too slow to dissolve.
• For making mortar, lime paint, or sludge treatment: Hydrated 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 potions. Get a 20-kilogram bag of feed lime or poultry lime, and you'll be set. Dose about 100 grams for every kilogram of feed, and calcium deficiency shouldn't be a problem anymore. In my own stable, I've noticed that regular Nordkalk feeding keeps the horses' hooves in better condition too – because calcium isn't just for eggshells.

We're fortunate in Finland to have our own lime industry that understands the country's soil and the needs of its animals. That's evident in every bag. When you buy local, you know what you're getting.