CHAPTER XV
HOW PORCELAIN IS MADE
We'll go to the slip-house first where the clay bins are," Mr. Marwood said to Theo, "that you may start at the very beginning of things. That is where the cars run in and unload the raw material."
They walked down a long corridor and rang for the elevator.
As the car shot to the basement Theo noticed a change in the appearance of the factory. On every floor they passed there was a hum of machinery and a glimpse of endless rows of china dishes; they stood on shelves; they covered tables; they were stacked one within another upon long counters.
"Some dishes, eh?" Mr. Marwood laughed, reading the boy's thought.
"I never saw so many in my life!"
"You will see many more before you are through," remarked his companion.
The elevator brought up with a jerk.
"Here we are!" exclaimed Mr. Marwood. "At least this is our way into the slip-house."
He led Theo through a passage and across a court into the adjoining building.
Here a white powder covered everything. Men who hurried by in overalls and caps were dusty as millers, their hands being coated to the finger tips with dried clay.
Mr. Marwood stepped forward into the long, cement-floored basement and pointed to the tracks embedded in it.
"It is on these tracks," he said, "that the cars come in and deposit their contents in the bins. The bins are of a pretty good size, you see. They measure about sixteen by thirty-two feet, and each one will hold eight car-loads of clay. After the different kinds of clay are unloaded and placed in their respective bins, the proper combination for specific varieties of porcelain must be weighed out and mixed in the 'blungers,' as we call the mixing tanks. Now this body formula, or clay combination, is not entrusted to the ordinary workman. It is kept secret. Therefore we have on the trucks that carry the clay between the bins and the blungers what we call charging-scales, which weigh automatically each ingredient in the compound without betraying it to the loader."
"That is pretty clever," replied Theo.
"Yes, it is a very ingenious device," Mr. Marwood agreed. "The blungers in which the clay is mixed are over there. You can see them—those great machines near the centre of the floor. They are heavy steel tanks lined with vitrified brick, and in the middle of each one is a revolving contrivance, with steel arms and teeth that grind the clay up very fine and blend it thoroughly. While it is being mixed in this way water is added to it, and also a certain amount of powdered oxide of cobalt to whiten it."
"Just as we put blueing in clothes," Theo ventured.
Mr. Marwood assented.
"This cobalt has already been pulverized and sifted most carefully, so there will be no particles in it, and so it will readily dissolve. After the clay mixture has had this mauling—for I can call it nothing else—the blunged compound, or slip, flows in liquid form into the sifter machines where it is strained through silk gauze or else a mesh of fine copper wire."
"I shouldn't think you could ever strain such stuff," Theo declared.
"The sifters do get very hard wear," answered Mr. Marwood, "and are the machines most liable to get out of order. They become clogged. Our sifters are self-cleaning. By that I mean they have an attachment which removes the waste obstructing them. Nevertheless, even with this improvement they still bother us at times. If you watch this sifting machine carefully you can see that the method is one of sliding the slip back and forth until it is forced through the straining ducts."
"And then what becomes of it?"
They walked on and stopped before another machine.
"This is a rough agitator," explained Mr. Marwood. "Into it is pumped the liquid slip you just saw strained, and afterward this is brought in contact with a series of horseshoe magnets which extract from the mixture every atom of iron."
"Iron?" repeated Theo.
"All clay has metals in it," continued Mr. Marwood. "Should you leave any of these in a pottery clay they would cause you much trouble, for when the ware was fired the metals would melt and discolor your porcelain. Sometimes this happens with cheap chinas. I dare say you yourself have seen dishes that are specked with yellow, or have stains here and there. Sometimes you can also detect bluish particles. That means the cobalt has not been properly ground or sifted. In less expensive wares such defects are frequent. But there is no excuse for them when making fine quality porcelains."
Theo listened attentively.
"After this iron has been extracted," went on Mr. Marwood, "the slip passes into smooth agitators, where it is simply kept well stirred in order that the heavier ingredients in it may not settle to the bottom. Then the liquid is forced by means of a slip-pump into the filter-presses, and it is now that you begin to see an approach to the clay used for shaping dishes. Up to this point the slip has been only a thick creamy substance. Now the filter-press squeezes this through canvas bags until after having been pressed between iron plates you get your cakes of smoothly mixed clay of about the consistency of putty. Each cake is of regulation size, and it is supposed to be an inch-and-a-quarter in thickness, and to weigh forty-two pounds."
"The clay is now ready for use?" Theo asked.
"Practically so," was Mr. Marwood's reply, "although before it can be sent to the jiggermen to be modeled it must pass through the pug-mill to be made more plastic and workable. It is here that it gets its final kneading, all the air bubbles in it being eliminated by a series of steel knives."
"I must say it is pretty thoroughly prepared," smiled Theo.
"It has to be," was Mr. Marwood's grave reply. "Each of these details is an important factor in the making of high grade porcelain, and should any of them be omitted we should get no flawless ware. It was this infinite care in preparing clay that gave to China, Japan, France, and Germany their perfect results in porcelain-making. If we would equal what has been done in the past we must be just as painstaking, and neglect no detail. As a nation we Americans are far too prone to dash ahead and expect results all in a minute. We do not like to mount a stairway step by step; we wish to shoot to the top in an elevator. Now you cannot manufacture porcelain, or for that matter anything else, in such a fashion."
"I know it," replied Theo. "Dad says we hurry so much over the little things that we turn out quantities of poorly made goods that are just hustled through instead of being carefully finished."
"Your father is right," Mr. Marwood admitted. "It is far too often quantity and not quality with us. Just so long as men are paid on the piece-work system we shall not better the condition, either. It stands to reason that a man who is rushing to make as many objects of one kind as he possibly can in an hour is not going to take the pains to finish them very carefully. His daily bread depends on his hurrying. Not a second can be lost. It is an unfortunate labor condition, and one that I hope to see remedied some time."
The elder man smiled.
"But we must not take time now to go into labor problems," he added. "In our day they are absorbingly interesting and one might spend hours discussing them. What we all are eager to do is to see them readjusted until they shall be fair to all parties."
"That is what Mr. Croyden wants," put in Theo.
"I know it is. He is heart and soul in this mill and his employees. All the time he is working to improve conditions here. Now we must go on, or we shall not get anywhere. To return, then, to our clay; it is now ready to be carried to the floor above on elevators and handed over to the potters."
"Are the ingredients for the glaze prepared in the same way?" Theo inquired.
"Partially so. The formula for the frit and glaze is also a secret one. Usually the frit, a material similar to glass, is crushed to powder beneath stone rollers called chasers. Water is then added and the compound turned into the grinding-mill where it is ground for an entire day. Sometimes, however, a different process is preferred and the material is put into a kiln and melted instead. In either case it must finally be worked into a smooth liquid which can be strained through fine lawn. It is then sent to the agitators and constantly stirred until it can be pumped into the storage tanks in the dipping-room."
"That is just what I wanted to know," said Theo.
The boy shook his head.
"Not now, thank you."
"Then as we have finished here shall we go up to the clay-shop?"
"Yes, I am ready," Theo affirmed. Then as if confronted by an afterthought he asked:
"Is the porcelain made here bone china or ——"
"Spar?" put in Mr. Marwood as the lad hesitated.
"I don't think I understand."
"Feldspar."
"Oh, then I know," cried Theo. "I did not realize you classified porcelains as bone or spar."
"We do," was the quick reply. "Our finest grade of porcelain has little or no phosphate of calcium, or ground bone, in it. But it is in consequence very costly, and therefore to meet the demands of the market we also manufacture a porcelain slightly strengthened with a bone element. Nevertheless this is composed of such a wonderfully blended body that it is as exquisite as any of the most beautiful English wares. Personally I prefer it to a pure feldspathic china.
"My questions are all answered now," laughed Theo. "Shall we go up to the clay-shop?"
They rang for an elevator and stepped in.
"Next floor, O'Keefe," said Mr. Marwood to the operator. "I am going to teach this lad how to make dishes."
