The key to preparing a waxy fleece is to scour it. My scouring method as below is suitable for all the waxy type fleeces, such as Merino, Polwarth, Halfbred and Corriedale. It is adapted from the three pot mini scouring plant that I observed at the Wool Laboratory at Massey University in Palmerston North.
Prepare fleece by laying staples in mesh bags or in the base of a plastic basket: a maximum of 170 gms (6 ounces) of fleece. Half fill a sink or tub with water at just over 70 degrees Celsius (160 degrees Fahrenheit) and dissolve 2 tablespoons of a mild laundry detergent (that does not contain enzymes or whiteners). A US equivalent is 2 tablespoons of Orvus. Press the bags or basket down into the water, which should be at 70 degrees Celsius after the fleece has been added.
Leave for three minutes, then carefully lift the bags or basket and press lightly to drain. Repeat with two more washes containing a similar quantity of powder or Orvus at 65 degrees Celsius (150 degrees Fahrenheit) and 60 degrees Celsius (140 degrees Fahrenheit). Then follow with three rinses in warm to hot water (the temperature is not crucial) – three minutes each. Squeeze, then lay to dry on a towel.
If you are using this method for the stronger fleeces that don’t contain wax the washes can be 5 degrees (about 10 degrees Fahrenheit) cooler. If in doubt use the higher temperatures. (A suitable thermometer can be purchased from any homebrew supply shop!)