condition, but should be no more than about 40 lb. for old insulation. If an atomizer is not available, the liquid may be applied by a cloth or paint brush, a brush being handier for getting into corners and be- tween small coils. Regardless of the method of application, care should be taken not to soak the insulation with the cleaning liquid. While the cleaning methods described permit the insulation to dry quickly at ordinary room temperatures, it is advisable to make certain that all moisture has been driven off by heating it as previously discussed under "Drying of windings" especially if varnish is to be applied. The application of a high-grade insulating varnish will renew the insulation and greatly prolong its life. The windings should be thor- oughly dried out, and the varnish applied while they are still warn. For oil or excessive dust conditions, a clear varnish should be used: but where excessive amounts of acid, alkali, or moisture are encountered, a plastic baking varnish is recommended. brushed on. The varnish may be sprayed or In the case of small rotors and stators, the most effective method is to dip the windings into the varnish. After varnishing, all metal parts adjacent to the insulation should be cleaned off with a varnish solvent. The windings should then be baked for 6 or 7 hours at a temperature not exceeding 90°C. The condition of the insulation, or the conditions under which the machine is to operate, may indicate a repetition of the foregoing varnishing and baking operations to be desirable. If time is at a premium and the mechine cannot be spared from service long enough for adequate baking, or if facilities are not available for baking, fair results can be obtained by applying a quick airdrying varnish which will dry in a few hours at ordinary room temperatures. 3-38