A method of treating substrates, such as wood, including the steps of applying an alkali silicate solution to one or more substrates and applying an alkali borate solution with boric oxide content to the substrates. The core comprises two end and portions in a single face of the electromagnet, wherein the two end portions constitute different poles of the electromagnet, and are shaped to be engagable with each of the teat cups in a close fit. The lock body includes a lock interface movable from a locking condition to an unlocking condition in response to proper user manipulation of the lock interface. After the desired location has been located, the retractor is placed into the surgical site and held in place in order to maintain the desired location for placement of the surgical implant, and the seeker is removed. The guide member includes a first portion corresponding to the transport unit and a second portion having a shape different from that of the first portion. The other inputs of the transconductance stages form the input terminals of the AC differential amplifier.