The Jacquard Mechanism – part one
For each row of weaving, the warp threads need to be separated to make the space for the shuttle with the weft to pass through. This post is about how the warp threads are raised and/or lowered to form the spaces for the shuttle. The space is called the shed. This is a term weavers use often when talking about things. When the shuttle is thrown through the shed, the weft thread is going over and under the warp threads: the “over, under” that is “weaving”. Remember the term: shed. You can see a good one in Part Three, Photo #5. [click photos to enlarge]
Photo #1 shows several looms in the studio where I took a 3-day workshop at the end of our tour: we call it “Lisio” but the full name is: Fondazione Arte Della Seta Lisio and is located in Florence, Italy.
All of the looms have the mechanism to make the sheds on top of the loom. Notice the loom with the ladder. Jacquard is the name of the mechanism. It replaced draw looms where a draw boy or girl sat on top or at the side of the loom to raise the required threads for the patterns.
The Jacquard mechanism works with punched cards that select which warp threads are to be raised or lowered.
There are needles in the mechanism and if a needle goes through a hole in a card, a warp thread is moved. Where there is no hole the warp thread stays at rest. One card is needed for each shed of weaving. For long repeats or big patterns many, many cards are needed because there are many rows in one repeat of the design. In photo #1 you can see some cards hanging at the top of the loom. They are seen in photos of the looms in previous posts, as well.
(Looms are similar to computers in that the warp threads are either up or down, which can relate to the 0’s and 1’s of the computer. Early computers used punch cards, too)
(If you zoom in you can see our cloth was all loops or uncut pile. That’s because we couldn’t be trusted to weave the threads tight enough to secure them into the foundation. If we had cut the loops and the pile threads were not secure enough in the foundation, we would have cut all the pile threads themselves. We were warned that the worst sound is hearing the weights from the spools drop to the floor indicating that all the threads were cut and were coming out of the loom. It could take weeks to get them all threaded into the loom again.)
Photo #3 shows the pattern graphed out on what is called point paper. Each horizontal row on the paper represents one card which is for one row of weaving, or one shed. We sat at a machine and punched the cards, making a card for each row of the pattern. We punched holes in 10 cards for the 10 rows of the pattern for the pile warp for our cloth.
Photo #4 shows the cards we punched being stitched together which will then go onto the Jacquard machine. Each card is for one shed for the insertion of one wire. A previous post has a photo of a wire being inserted in one of the sheds for the cloth we wove. Photo #5 shows our teacher on top of the loom, putting our cards into the Jacquard mechanism.
More about the mechanism in the next post.