The two primary ingredients of a mushroom "casing" mix are: Peat & Vermiculite.
(NOTE) Coir is sometimes used in "casing" mixtures.
Dependent on the source; the pH of "peat" can range from 3.5 to 6.
Dependent on the source; the pH of "vermiculite" can range from 6 to 9.
(Dependent on the source; the pH of "coir" can range from 5,5 to 7.5.)
The preferred pH range of a casing mixture is 6.5 to 8. 7.5 is optimal.
Given these pH variables, it is not practical to create an optimal pH "casing mix" by adding so many "parts" of peat, vermiculite, coir & a calcium carbonate buffering agent.
If you wish to achieve optimal results when adjusting pH, it is highly advisable to use litmus strips (with color chart), or acquire a pH test probe (available at most garden supply stores, under $20) to accurately test, and adjust the pH of your casing mix, prior to application.
Doing all other cultivation steps properly, then applying a casing mixture outside the proper pH range, most often creates poor cropping results.
The long story:
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Peat is a fibrous organic compound found in bogs that is formed by the partial decomposition of plants in the acid water of the bog. Peat is a compact, dark brown organic material with a high carbon and represents the first stage in the transformation of vegetation into coal. Peat bogs are distributed throughout the world; extensive deposits are found in North America, Russia, the Scandinavian countries, England, and Ireland.
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Vermiculite is the geological name given to a group of hydrated laminar minerals which are aluminum-iron magnesium silicates which have the appearance of mica, and is found in various parts of the world. When processed for horticultural use, the mineral is subjected to intense heat, expanding it into accordion-shaped granules with countless layers of thin plates.
The pH, color and chemical composition of vermiculite will vary depending on the source from deposits around the world.
TYPICAL PHYSICAL PROPERTIES OF EXFOLIATED VERMICULITE
Color: Light to dark brown
Shape: Accordion-shaped granule
Bulk density (a): 64-160 kg/cu m
4-10 lb/cu ft
Moisture [Email]loss@110[/Email] ?C (230 ?F): 4-10%
pH (in water): 6-9
Combustibility: Non-combustible
MOH Hardness: 1-2
Sintering temperature: 1150-1250 ?C
2100-2280 ?F
Fusion point: 1200-1320 ?C
2200-2400 ?F
Cation exchange capacity (b): 50-150 me/100g
Specific heat: 0.84-1.08 kJ/kgK
0.20-0.26 kcal/kgK
0.20-0.26 Btu/lb F
Waterholding capacity (a): 220-325% by wt
20-50% by vol
Notes: (a) Bulk density and water holding capacity vary with article size.
(b) Exchangeable ions are Mg+2 and Ca+2, sodium acetate saturation / ammonium acetate substitution method.
(Source) http://www.vermiculite.org/properties.htm
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Coir is typically processed from ripe coconut husks which are dark brown in color and have been retted in freshwater for three to six months. The retting process of coconut husks acts as a curing process for fiber in coconut husks. Curing in freshwater increases resistance to UV (ultraviolet) degradation and also increases the flexibility of processed fiber without causing deterioration.
During traditional processing, coconut fiber from cured husks is separated by skilled labor into grades depending on the length of fiber. The longer and stronger fibers are called bristle coir and the shorter and thinner fibers are called mattress coir (Santha, 1994). Coir processed from ripe husks cured in freshwater is dark brown in color.
When the ripe coconut husk is dry, it is an excellent firewood. As a result in countries with a high population density, most of the ripe brown coconut husks are used for firewood and the coconut husks available for processing coir are unripe green husks. Unripe green coconut husks are usually soaked in brine to make the coir processing easier (Meerow, 1997).
An economical way to soak coconut husks in brine is to use lagoons (Nedia Enterprises, 1996). Coir processed from lagoon-cured green husks is light brown or white in color. This coir is referred to as white coir. Salt in lagoon water makes it easier to process unripe green coconut husks.
Needless to say, fibers in coir processed from unripe green coconut husks are not fully mature compared to fibers coming from ripe brown coconut husks. Lagoon-cured brown coconut husks also produce white coir. Salt in lagoon water acts as a bleaching agent that can weaken coir used in field applications. White coir is, therefore, much weaker than brown bristle coir processed from ripe brown husks.
High demand for coir has led to new coir processing methods which may produce a weaker product than the traditional freshwater-curing process. Mass-scale coir manufacturers recently implemented coconut husk defibering machines. These machines can separate fiber from uncured or partially-cured husks or unripe green husks or ripe brown husks.
Advantages of these defibering machines to the coir producer include reduced expense and faster production rates since skilled labor is not required and the six-month curing time is reduced or eliminated.
Some of these mass-scale coir manufacturers go further and soak unripe green husks in a bacterial solution and process for white coir within 72 hours of curing (Joseph and Sarma, 1997). These machines do not separate fiber into bristle coir and mattress coir but yield a mixture of long and short (strong and weak) fibers.
A quick way to produce white colored coir for decorative coir products is chemical bleaching of the coir. In chemical bleaching, brown or light-brown colored coir is treated with chemicals to remove the brown color. Chemical bleaching may have some negative effects on the strength and durability of coir. On the other hand, coir from the ripe husk is well known as a natural fiber and the rich brown color is more attractive than a white color for erosion control applications. Most importantly, addition of chemicals to natural coir may create a potentially hazardous situation in many environmentally sensitive applications.
Experience with coir in the agricultural industry has shown that only the traditional brown bristle coir which is processed from ripe brown coconut husks cured for at least six months in freshwater has performed well in applications where durability and strength retention are critical for satisfactory field performances.
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"pH", is a measure to describe the acidity of a medium. pH 7 is neutral; higher means alkaline, lower acidic.
Peat is a major constituent of preferred casing mixes. The pH of peat is variable, dependent on the source it came from. Meaning, the pH of peat differs from various sources.
The preferred pH range of a casing mixture is 6.5 to 8. 7.5 is optimal.
Peat is acidic. Consequently, to achieve an optimal pH range of a casing mix, the pH of the casing mixture must be adjusted accordingly (within the range of 6.5 to 8).
The pH of the casing must be within certain limits to support strong mycelial growth. An overly acidic or alkaline casing mixture will depress mycelial growth and supports unwanted competitors.
It is generally easier to make casing materials more alkaline (i.e., increasing the pH) than it is to make them more acid (i.e., reducing the pH).
A movement of 0.5 is easy but, because the pH scale is logarithmic, a movement on the order of, 2.0 points becomes more difficult because there is a factor of 10x between each full point, so pH 5.0 is actually 100 times more acid than pH 7.0.
There are several common types of lime available for use, though care should be exercised with all of the products. Lime is caustic and a skin and eye irritant and can be dangerous if misused. If you choose to use such products, carefully read and follow all manufacturer directions exactly.
The major types of lime products include:
Hydrated Lime: fast acting, but not long lasting. It is very effective to produce a fast change in pH level. It is also the "strongest" form of lime generally available, and you must follow all manufacturer precautions, since your skin and eyes can be easily irritated or burned if the product is misused.
Ground Limestone: a naturally occurring type of limestone that has been ground to a fine powder. How quickly it will act to modify pH and how long it will persist depends on how finely it was ground.
Generally, ground limestone is weaker than hydrated lime, needing about 30% more to raise the pH by the same amount. It has the advantage, however, of usually being significantly cheaper than the hydrated lime, and usually works more slowly and lasts much longer.
Mixed Lime: usually sold under a brand name. Most brands contain a variety of particle sizes to provide some immediate benefits, as well as a longer persistence. (this is often referred to as "time released" lime).
pH gradually falls to less than optimal by the end of cropping due to acids secreted by the mushroom mycelium. Consequently, a long lasting buffering agent is preferable.
If you wish to achieve optimal results when adjusting pH, it is highly advisable to use litmus strips (with color chart), or acquire a pH test probe (available at most garden supply stores, under $20) to accurately test, and adjust the pH of your casing mix, prior to application.
Doing all other cultivation steps properly, then applying a casing mixture outside the proper pH range, most often creates poor cropping results.
6T (aka Mycota) 
--------------------
~whiskey river rafting, hot tubbing, dirty dancing & spending money on - wild women - having fun & just gonna waste the rest~
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