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

If you've ever wondered why eggshells from one farm hit the pan with a satisfying crack, while on another they crumble in your hands before you even get them to the pot, the answer is often as simple as it is surprising: lime. Or, more precisely, its quality and how it's used. Here in Finland, there's one company that's been doing this work for decades, supplying barns, stables, and construction sites alike – 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 purpose. Not to mention that not all lime is created equal. It's a raw material with hundreds of different uses, ranging from what goes into animal feed to what gets mixed into mortar when building a new house.

From Finnish stone to the chicken bowl

When you walk down the aisle of an agricultural or hardware store and see the Nordkalk display, 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 around 36 per cent, and most importantly – it contains no unnecessary additives. Animals need calcium for the same reasons humans do: 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 simply comes down to coarseness. The feed lime is ground to a fineness of about 1 to 1.5 millimetres. It dissolves quickly and is therefore well-suited for mixed feeds for cattle, pigs, and horses, but also for chickens if you're fermenting their food yourself. Poultry lime, on the other hand, is a coarser grit, about 3 to 6 millimetres in size. It dissolves more slowly, and that's exactly 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, maintains calcium availability throughout the eggshell formation period. Offered in a separate container.
• Chick Lime (3 mm): Coarser than feed lime but finer than poultry lime. Suitable for growing pullets.

When it comes to feeding chickens, remember that calcium deficiency doesn't show up all at once. It shows up when you notice one day that a bird seems a bit sluggish, 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 right on the mark, and there are no stones or impurities in the bag.

Construction lime is no joke

Now, let's move to the other end of the spectrum. When we're talking about Sammutettu Kalkki Nordkalk Sl 90 30kg, we're no longer in the chicken coop; we're in a whole different world. This is serious construction 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 reaction that generates intense heat.

This is a product you don't mess around with. As the product label warns, it irritates 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 sourced from Gotlandic limestone as a raw material, but it's processed in Finland. It's ground and hydrated to just the right consistency to produce a strong, long-lasting mortar. For builders, it's a reliable choice when traditional durability is what you're after.

Rocks and minerals – so much more than just dust

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

What's interesting is that we're now starting to grasp the importance of the circular economy for these stones. The mining industry is increasingly talking about conflict minerals, but here in Finland, the focus has shifted to how we reuse 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 specifically to develop this field.

So, it's not just about sweeping up stone dust in the barn. This is about building for the future, where minerals, like dicopper chloride trihydroxide or even concretion-type iron and manganese deposits, find new uses. And best of all, the same principle applies on the farm: when the eggshell is strong, it's a sign that the calcium cycle is working.

How to choose the right bag?

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

• For a horse or large cattle: Nordkalk Ruokintakalkki 20kg, mixed into feed or mash.
• For laying hens: Nordkalk Aito kanakalkki 40 kg, offered in a separate container for free-choice feeding or mixed into a homemade feed mix.
• For young chicks and growers: Chick Lime (3 mm), which has enough grit without being too slow to dissolve.
• For making mortar, lime paint, or sludge treatment: Sammutettu Kalkki Nordkalk SL 90 30kg, but don't forget your protective gear.

And one final tip: if your hens' eggshells are starting to thin out, you don't need any fancy little packages. Get a 20-kilo bag of feed lime or poultry lime, and you'll be set. 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 feeding with Nordkalk keeps the horses' hooves in better condition too – that calcium isn't just for eggshells, after all.

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