P3 is an underglaze suspended in oil and can be used with a crowquill pen for precise application of fine black lines. Sold here as a set including a small vial of P3 which can easily be maintained in a usable mixture, pen holder and two small nibs. Using P3 in a pen is an acquired skill. Go slow and steady. May be cleaned up with alcohol. Apply on top of fired layer of enamel. Dry thourally, fire at 1400 degrees, then fire layers of transparent over P3.