{"product_id":"gypsum-chalk-premixed-calcium-supplement-for-mushroom-substrate-bags","title":"Premixed Calcium Supplement for Mushroom Substrate","description":"\u003ch2\u003eStop fighting clumping. Start growing better bags.\u003c\/h2\u003e\n\u003cp\u003ePremixed Calcium Supplement is a precision-blended, ready-to-use calcium supplement for mushroom bulk substrate bags. Combining organic calcium sulphate (gypsum\/CaSO4) and calcium carbonate (chalk\/CACO3) in a single premix, it solves two of the most common substrate headaches at once — clumping and pH drift — so your bags colonise cleaner and faster.\u003c\/p\u003e\n\u003cp\u003eBulk discount up to 20% off on larger orders!\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eKey Benefits:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eReduces clumping\u003c\/strong\u003e — calcium sulphate keeps substrate particles separated and workable, improving mycelium penetration throughout the bag\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHelps maintain balanced pH\u003c\/strong\u003e — calcium carbonate (chalk) acts as a natural buffer, supporting a stable environment for healthy colonisation\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDouble calcium boost\u003c\/strong\u003e — both calcium sulphate and calcium carbonate contribute available calcium, a key mineral for strong mycelial growth\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePremixed and ready to use\u003c\/strong\u003e — no guesswork, no separate measuring of two powders, just scoop and add\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatible with all common bulk substrates\u003c\/strong\u003e — hardwood, straw, coco coir blends and Masters Mix\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSimple, consistent application\u003c\/strong\u003e — clear dosing rates for small and large bags\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eWhy Calcium Sulphate and Calcium Carbonate Work Together:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eCalcium sulphate (gypsum) is the workhorse of substrate conditioning. It improves particle separation, reducing the dense clumps that block gas exchange and slow mycelium spread. It also adds calcium without significantly shifting pH — making it safe to use alongside other additives.\u003c\/p\u003e\n\u003cp\u003eCalcium carbonate (chalk) complements gypsum perfectly. It acts as a gentle pH buffer, helping to counteract the slow acidification that can occur during sterilisation or pasteurisation and throughout colonisation. It also contributes an additional source of calcium, giving your mycelium the minerals it needs to thrive.\u003c\/p\u003e\n\u003cp\u003eTogether, they create a more forgiving, better-structured substrate that colonises evenly and supports healthier, more productive grows.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eApplication Rates:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge bags (2.2 – 2.5 KG substrate):\u003c\/strong\u003e 2 tablespoons \/ 40g per bag\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSmall bags (1 – 1.6 KG substrate):\u003c\/strong\u003e 1 tablespoon \/ 20g per bag\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eMix thoroughly into dry substrate before hydrating and sterilising or pasteurising as normal.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eHow Much Will One Bag Treat?\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eAt 40g per bag → approximately \u003cstrong\u003e25 large substrate bags\u003c\/strong\u003e per 1KG of Gypsum + Chalk\u003c\/li\u003e\n\u003cli\u003eAt 20g per bag → approximately \u003cstrong\u003e50 small substrate bags\u003c\/strong\u003e per 1KG of Gypsum + Chalk\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat mushrooms is Gypsum + Chalk suitable for?\u003c\/strong\u003e\u003cbr\u003eIt's suitable for the full range of commonly cultivated species — oyster mushrooms (all varieties), lion's mane, shiitake, chestnut mushrooms, and most other wood-loving species grown on bulk substrate bags.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs it safe to use with sterilised and pasteurised substrates?\u003c\/strong\u003e\u003cbr\u003eYes. Gypsum + Chalk is added to your dry substrate before hydrating, then sterilised or pasteurised along with everything else. Both calcium sulphate and calcium carbonate are heat stable and will not degrade during the sterilisation or pasteurisation process.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use too much? Will it affect my pH badly?\u003c\/strong\u003e\u003cbr\u003eAt the recommended rates, Gypsum + Chalk is well-tolerated and won't push pH to harmful levels. Calcium carbonate is a mild buffer rather than a strong alkali, so it raises pH gently. Stick to the recommended dosing and you'll be in a safe range for most species.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDo I need to add any other pH adjusters if I use Gypsum + Chalk?\u003c\/strong\u003e\u003cbr\u003eFor most standard bulk substrate recipes, Gypsum + Chalk at the recommended rate provides sufficient buffering without needing additional pH adjusters. If you're using an unusually acidic substrate or supplementing heavily with high-nitrogen additives, you may want to test your substrate pH after hydrating.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs this food-grade?\u003c\/strong\u003e\u003cbr\u003eNo, both calcium sulphate and calcium carbonate used in this blend are not food-grade minerals.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow should I store it?\u003c\/strong\u003e\u003cbr\u003eStore in a cool, dry place away from moisture. Keep the bag sealed between uses. Properly stored, it has an indefinite shelf life.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it clump itself during storage?\u003c\/strong\u003e\u003cbr\u003eThe calcium sulphate content helps resist clumping in the product itself. If stored in a dry environment, it should remain free-flowing and easy to scoop.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it affect the smell or taste of mushrooms?\u003c\/strong\u003e\u003cbr\u003eNo. At these application rates, Gypsum + Chalk has no detectable impact on the flavour or aroma of your mushrooms.\u003c\/p\u003e","brand":"Kai Kai Farm","offers":[{"title":"Default Title","offer_id":52128683262263,"sku":"MS-GC-1KG","price":7.0,"currency_code":"AUD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0791\/2040\/0695\/files\/Gypsum_Chalk_Precision_Blend_Mushroom_Substrate_Stop_Clumping.webp?v=1781066887","url":"https:\/\/kaikaifarm.au\/products\/gypsum-chalk-premixed-calcium-supplement-for-mushroom-substrate-bags","provider":"Kai Kai Farm","version":"1.0","type":"link"}