as given by Ehrenfried Pfeiffer, circa 1938
by Hugh Courtney

Keep the Horn Silica (BD501) powder in any dry, sunny place until needed. This preparation keeps indefinitely if dry. Spray it only on areas where Horn Manure (BD500) 
has been previously applied.

Timing        
• Used only after plant roots are well established
• Never applied before transplanting
• Applied in the early morning when there is no wind
• Generally applied in the late spring or early summer when warmer weather is well established
• Never used when there is danger of frost
• Applied just before a rain is not recommended, however, it is likely that a light rain is not of consequence. Once BD501 is applied, its forces are already at work.
• Applied to mature seedlings (2nd/3rd leaves unfolded)
• Never used on young evergreens or fruit trees
• Used when pests have destroyed much foliage
• Used only on trees after they have blossomed when the blossoms come before the leaves
• Used especially during wet seasons with little sunshine
• Indoors/greenhouses during the shortest days of the year

Preparing for Stirring    
• One portion (¼ to ½ teaspoon or 2.5 to 3 grams) of 
  BD501 added to 3 gallons/11.4 litres of warm, clean, uncontaminated rain or other water
• Use a clean container large enough to prevent splashing

Stirring
• Stir with a light-weight, strong stick
• Vigorously stir in one direction until the liquid forms a deep crater or vortex
• Quickly reverse direction and repeat vigorous stirring
• Alternate the directions of stir every minute or so and continue stiring for one full hour
• Stir so the direction of the stick movement is towards your heart

Spraying
• If using a spray device, filter the stirred liquid using clean cheese cloth to avoid clogged nozzles
• Spraying is done as soon as possible after stirring
• The Horn Silica deteriorates rapidly upon standing
• If left overnight it is useless
• Apply in an upward direction to the foliage
• Use clean utensils; chemical residues make it useless
• Apply in a fine mist spray using a sprayer device
• One portion in 3 gallons/11.4 litres will cover an acre

Hugh Courtney - Writer, Mentor, Teacher, Researcher 

In addition to contributing articles, Hugh Courtney has taken on the advisory role of forecasting favourable and unfavorable times for this calendar. He has devoted more than 40 years to perfecting the art of making biodynamic preparations. Taking a cue from his own mentor, Josephine Porter, who declared, “These preparations are no secret, I will teach anyone who wants to learn how to make them,” he has mentored hundreds of people on the finer points of making quality preparations. 

Ever concerned about keeping this special art form alive into the future, in 2009, Hugh founded Earth Legacy Agriculture, LLC to provide quality preparations for discerning practitioners. www.earthlegacyagriculture.com