Overshot is a two shuttle weave structure, where one shuttle of weft weaves a plain weave fabric while the second shuttle carries a heavier weft which floats over areas of warp to create what is known as "pattern". This heavier weft also floats under areas of warp for what is called "background". Where there is pattern on the face of the cloth, there will be background under that, and vice versa. The heavier weft also weaves over and under warp ends either side of the pattern float to hold it in place. This creates stripes known as "half tones". When designing a profile draft, the blocks in the drawdown section represent the weft floating over warp ends. The half tones on either side of the pattern floats are not shown in the profile draft mode. There are many excellent references on drafting overshot. However, for a beginning weaver, the rules can seem daunting. Because I like to design my work in profile draft mode, and then translate the profile draft to a thread by thread drawdown, I have devised a different way to draft the classic 4-block overshot weave structure.
Look at the five Profile Drafts below which represent variations on a diamond motif. There are four sections in each draft which contain black squares the Profile Threading Draft, the Profile Tie-up of blocks, the Profile Treadling plan, and a Drawdown where blocks represent the pattern floats on a plain weave background.
It's easy to determine from a Profile Draft how many warp ends will be in a threading draft. Look again at Profile Draft I. There are nineteen threading blocks. Multiply nineteen blocks by three warp ends per block for a total of 57 warp ends. If this size is too narrow for the intended purpose of the fabric, a single unit threading block can be increased by a pair of warp ends so that there are five warp ends per block. For this increase, Block 1 is threaded 1-2-1-2-1; Block 2 is threaded 2-3-2-3-2; Block 3 is threaded 3-4-3-4-3; and Block 4 is threaded 4-1-4-1-4. Each additional pair of threads has been highlighted in red. This increases the number of warp ends by 60 percent to 95 warp ends. Blocks can also be reduced in size by subtracting a pair of warp ends in a block. In this case, three warp ends, reduced by a pair of ends, makes each threading block one warp end only. Block 1 is threaded on shaft 1, Block 2 on shaft 2, Block 3 on shaft 3, and Block 4 on shaft 4.
Notice there are five points in the Profile Threading of Draft I where the draft reverses its course - twice at Block 1 and three times at Block 4. These reversal points are called "turning points". These turning points are also places where a pair of warp ends can be added or subtracted to increase or decrease the overall size of the finished fabric.
In Profile Drafts III and IV, the center turning Block 4 is one unit in width. This implies that three warp ends are threaded on shafts 4-1-4. However, a single unit block can be increased by a pair of warp ends, enlarging the block from three to five ends; or it can be decreased by a pair of warp ends, reducing the size from three ends to a single end. In this case, a pair of extra ends has been added to the center turning Block 4 in Profile Drafts III and IV indicated by the red arrow.
Draft IV contains both double sized blocks and single unit blocks. Double sized blocks imply seven warp ends per block which can in turn be enlarged by a pair of threads to nine warp ends; or a double sized block of seven ends can be reduced by a pair of ends to five ends per block. This flexibility in block size allows the weaver the ability to customize the size of a draft to fit the requirements of a finished design.
In Draft IV, the double sized blocks have been reduced by a pair of warp ends, from seven to five threads. Since there are fourteen double sized blocks, this reduction in block size decreases the threading draft by a total of 28 ends. The single unit blocks still contain three warp ends per threading block with the exception of the center turning Block 4 which has a pair of ends added to make it five ends. The turning block is indicated by the red arrow.
A quadruple sized block for Block 1 will be 121 - 121 - 121 - 121. Add the missing shaft 2 between the warps threaded on shaft 1 and the correct threading for a quadruple sized block will be 15 ends 121 2 121 2 121 2 121. Again, a block can be reduced to 13 ends or increased to 17 ends depending on the length of float desired.