It should be noted, however, that this refinement is necessary only in extreme cases. In process pro duction, as under the production-order method, goods should, in general, be shipped as soon as possible after completion. It is not possible to hold all the goods manufactured during an accounting period till the end of that period, so as to be able to compute ac curately the cost of production; therefore, this cost must generally be computed upon the basis of expe rience in manufacturing similar goods. It will be noted, also, that many expense items can be allocated only approximately ; and, where more than one line of goods is in process, accurate allocation is as diffi cult under the process-production system as under the production-order method. No definite rules can be laid down for these more complex process methods; each problem must be studied independently, indi vidual judgment entering largely into the solution of the problem involved in each set of conditions.
9. Other difficulties of process-accounting.—The discussion assumes that the processes considered are continuous, and that all the material of each kind passes thru the same series of machines. If the combination of machines and processes varies from day to day, all the difficulties discussed under the pro duction-order method appear at once. If this takes place, even tho there may be some semblance to con tinuous production, it is better to pass the material thru in lots, assigning a production order to each lot.
Even then, there will be forms of process production that will be troublesome to the cost finder.
In intermittent industries, for instance, there are processes which are continuous in character, and which use considerable expense material the cost of which is difficult to allocate. Processes where material is dipped in insulating fluid—japanning and baking processes, etc.—are instances of this kind. In proc esses like cement-making it is possible to weigh the material, and to use the weight as a measure of labor and expense. But in processes like those others just mentioned, such a measure of labor and of expense ma terial is difficult to obtain. Thus, in plating or dip ping, the superficial area of the material treated is the proper criterion for measuring expense material, and this area is difficult to obtain. The expense ma terial itself may be measured, but here again more than one kind of product may be treated at the same time, a condition which makes the allocation difficult if not impossible. Similar remarks apply to baking processes where several kinds of products may be baked simultaneously, and where the accurate alloca tion of direct labor and indirect expense may be im possible. No rules can be laid down for complex cases like these, but a knowledge of correct principles, com bined with good judgment, will always-indicate com promise methods that will give results, accurate enough, without too much complication.