Cement Work, I

Cement Work, I.

The mould closed, showing method of tamping.

The tamping or pressing down of the moist mixture into the mould is a simple process and yet it must be done with some care. A good handful of the mixture is thrown into the mould so that it will fall between the core and the sides. With a stick made of ordinary hard wood and having about the dimensions of a foot rule, only a little thicker, the mixture is pounded or tamped down hard. It is well to scratch the upper surface of the tamped cement with a pointed stick, so that the next handful when tamped will unite with the one before. This process goes on until the open top of the mould is reached. It is then well to pile up the mixture an inch or so above the level of the mould and to press it down hard by striking with a mallet over a smooth board. The last layer, which will form the bottom of the flower pot, must be smoothed off carefully with a trowel or straight edged stick; otherwise the pot will set unevenly. It often happens in taking off the mould that some corner or small section of the flower pot will crumble and fall off. If this broken place is not too large, it can be easily mended by patching a little of the mixture into the defect in much the way a dentist fills a tooth.

When the cement is tamped in, the walls of the mould will leave their impress on the mixture and the core will fill up the space which will later become the inside of the flower pot. As soon as the tamping is finished, the sides of the mould are removed with great care to avoid breaking down the corners or the decoration. The finished flower pot is then lifted on its carrier, leaving the core behind on the table. The pot on its carrier is then placed somewhere out of danger of touch, and it must be kept moist for the first twenty-four hours while the cement is setting. Moisture may be provided by the use of little tents of wood covered with cloth. These tents, placed over the soft flower pot and kept moist with water will be very useful. After about twelve to twenty-four hours the flower pot will be hard enough to be lifted from the carrier. It may then be placed upon the ground or the floor or some suitable shelf where it must remain as nearly undisturbed as possible for at least two weeks, being kept moist all this time. It is then ready for use, although a longer hardening process will do no harm. After the first few days it is well to turn the pots over, right side up, and to fill or partly fill them with water. This insures a thorough soaking. So much stress is laid on wetting and keeping dry because if the pots are allowed to dry, especially during the first few days, they will always be weak and crumbly.

Cement Work, 2. Opening the mould

Cement Work, 2. Opening the mould - showing flower pot upside down, core still in place inside.

The small iron moulds meet the requirements of a considerable field of cement work and the method is particularly useful for those whose physical strength is slight and whose nervous energy quickly gives out. They produce, however, only comparatively small pieces. Cement is a material well adapted for larger and heavier work. In making the larger pieces such as bay tree pots and the larger hollow ware for the garden, the so-called template process is more practical. To make one of these larger pieces the same mixture of sand, cement, and coloring matter is mixed, only in larger amount. The core, which is to represent the inside of the large pot, can be made of sheet metal, in plaster of Paris, or in moulder's sand which last may be fashioned into any shape after it is moistened. This core is fitted over a central shaft which protrudes well above the top of the core. The core naturally follows the lines which are to be the outside of the pot but need not follow exactly. This core should be made or fixed upon a solid table and the central shaft must be screwed or bolted to the table firmly. Over the core may then be plastered or tamped a sufficient amount of the moist cement material to cover the whole surface an inch or two deep. The tamping is made easily practical by placing around the core a sheet metal apron or guard which will hold the material firmly while the tamping is going on. This sheet iron apron can be made by any tinsmith and it should be built in two parts so that when the tamping is done the metal may be easily removed from the mass. When the apron is removed, there will remain the core covered thickly and firmly with the tamped cement mixture, which is still soft enough to be scraped or moulded into shape. Through the middle of the whole structure protrudes the central shaft. The template or cutter, which is to shape the outside of the pot, is made of steel or iron cut to the exact lines that are required for the outside of the pot. It fits over the central shaft in such a way that it may be revolved about the piece, cutting slowly into the mass. It is adjusted so that the cutting edge shaves off a little at a time until the final shape is secured. If the mass is cut down too rapidly, it breaks and falls to pieces. When the cutting is done, the template is removed and the piece is allowed to remain over night or longer, resting on the core. The material is kept moist by the application of cloths applied in many thicknesses and soaked with water. Finally the core and its cement shell are turned over and the core removed. These larger pots, like the smaller pieces, must then be kept moist for a considerable period of time, two weeks or more, until the hardening process is complete. The hole in the bottom of the pot, left by the shaft, may be plugged with moist cement which will later harden.

Cement Work, 3

Cement Work, 3.

Lifting the completed flower pot from the core which is left behind on the table. The pot is still soft but is movable because it rests on the little frame of metal called the carrier.