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bluehelix · 02-01-06, 16:40

Hydrated lime should not be used. Calcium carbonate should be used to balance out peat moss. The only people using hydrated lime are hobbyists, and depending on the grade and exactly how much one uses, it could be a total disaster. Some grades of hydrated lime are extremely caustic and strong.

No mushroom farm in existence would use hydrated lime. In fact I challenge anyone to find me a single mycological text referring to it for casing pH balancing. There are numerous reasons why to not use it for this purpose. First, it has a pH of about 12.5 which means it can very easily create way too basic of a casing, burning the mycelium and killing it. With peat varying so much in its pH, there is no sensible way to use calcium hydroxide (hydrated lime) because one doesn’t know how much to add unless one has a very good pH probe, which cost about $100 to $150. Secondly, hydrated lime converts to calcium carbonate, a weaker base, upon a reaction with the air. This can take days or weeks depending on the amount of exposure and how much water is present. In the case of a casing, it would likely be about a week. After all the hydrated lime converts to calcium carbonate, the pH will fall. In the later flushes, the pH would continue to fall unless calcium carbonate chips of some sort were used. Calcium carbonate doesn’t lose its buffering ability so easily like that.

If one intends to use hydrated lime, it must be used (a) with a sensitive pH probe to monitor the casing since peat varies in pH a lot and the mix can easily become too basic, and (b) with the aid of some chip or powder form of calcium carbonate which can hold the pH up in the long run. I don't use hydrated lime at all. It's not used by the pros, and I see no benefit over using regular calcium carbonate which is the gentle buffer that is normally used.

Calcium carbonate powder can be purchased in the many forms. You can find it in a reasonably pure form at some garden stores sold as “garden lime” in the form of ground oyster shells, but read the label: you are looking for ground oyster shells, limestone, or any other form of calcium-carbonate-based lime, not dolomite-base lime (which is a magnesium-rich form). Another place to find pure calcium carbonate is from wine making shops. Call some home brewer shops and ask for calcium carbonate powder; they’ll know what you want. Another method to derive it from hydrated lime is to spread your hydrated lime no more than about ½ inch thick on the bottom of 13"x8" glass pan (do NOT use a metal pan), and cook at 350F for about an hour. The heat and CO2 in the air will covert most if not all of the hydrated lime to calcium carbonate.

02-01-06, 16:40	#2 (permalink)
bluehelix Mycotopiate Join Date: Jul 1972 Posts: 516	Hydrated lime should not be used. Calcium carbonate should be used to balance out peat moss. The only people using hydrated lime are hobbyists, and depending on the grade and exactly how much one uses, it could be a total disaster. Some grades of hydrated lime are extremely caustic and strong. No mushroom farm in existence would use hydrated lime. In fact I challenge anyone to find me a single mycological text referring to it for casing pH balancing. There are numerous reasons why to not use it for this purpose. First, it has a pH of about 12.5 which means it can very easily create way too basic of a casing, burning the mycelium and killing it. With peat varying so much in its pH, there is no sensible way to use calcium hydroxide (hydrated lime) because one doesn’t know how much to add unless one has a very good pH probe, which cost about $100 to $150. Secondly, hydrated lime converts to calcium carbonate, a weaker base, upon a reaction with the air. This can take days or weeks depending on the amount of exposure and how much water is present. In the case of a casing, it would likely be about a week. After all the hydrated lime converts to calcium carbonate, the pH will fall. In the later flushes, the pH would continue to fall unless calcium carbonate chips of some sort were used. Calcium carbonate doesn’t lose its buffering ability so easily like that. If one intends to use hydrated lime, it must be used (a) with a sensitive pH probe to monitor the casing since peat varies in pH a lot and the mix can easily become too basic, and (b) with the aid of some chip or powder form of calcium carbonate which can hold the pH up in the long run. I don't use hydrated lime at all. It's not used by the pros, and I see no benefit over using regular calcium carbonate which is the gentle buffer that is normally used. Calcium carbonate powder can be purchased in the many forms. You can find it in a reasonably pure form at some garden stores sold as “garden lime” in the form of ground oyster shells, but read the label: you are looking for ground oyster shells, limestone, or any other form of calcium-carbonate-based lime, not dolomite-base lime (which is a magnesium-rich form). Another place to find pure calcium carbonate is from wine making shops. Call some home brewer shops and ask for calcium carbonate powder; they’ll know what you want. Another method to derive it from hydrated lime is to spread your hydrated lime no more than about ½ inch thick on the bottom of 13"x8" glass pan (do NOT use a metal pan), and cook at 350F for about an hour. The heat and CO2 in the air will covert most if not all of the hydrated lime to calcium carbonate.