Block Design - Overshot

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.

Look at the five Profile Threading Drafts. They range in width from 19 blocks in Draft I to 38 blocks in Draft V. Draft I is comprised of blocks that are equal sized units, just one unit in width for each block. Drafts II to IV have single and double sized blocks, while Draft V is a mixture of single, double, triple, and quadruple sized blocks. The blocks in the Profile Threading Drafts are in four different rows. Calling the blocks by numbers will make the threading more intuitive. Blocks are called 1,2,3 and 4 rather than A,B,C and D. Blocks in the bottom row are labeled Block 1, and numbered sequentially so that blocks in the upper row are labeled Block 4.

Begin with Draft I. The quick and easy formula for threading is that each single block in the Profile Threading Draft represents three warp ends threaded alternately on two shafts. The three warp ends for Block 1 are threaded on shafts 1-2-1; the three warps for Block 2 are threaded on shafts 2-3-2; the three ends for Block 3 are threaded on shafts 3-4-3; and the three warps for Block 4 are threaded on 4-1-4. Notice that a block threaded on three warp ends begins and ends on the same shaft as its Block number. So Block 1 begins and ends on shaft 1, Block 2 begins and ends on shaft 2, Block 3 begins and ends on shaft 3, and Block 4 begins and ends on shaft 4. The threading for Profile Draft I appears below.

Notice that there is a strict alternation of odd and even ends throughout the weaving draft. This is crucial since the main foundation cloth of overshot is a plain weave fabric where ends alternate in the raised and lowered positions.

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.

Drafts II, III and IV contain single unit and double sized threading blocks. Following the example above, if there is a double sized block called Block 1, it should be threaded 1-2-1, 1-2-1. But is that right? Notice there are two warp ends that are threaded side by side on shaft 1. This cannot happen because plain weave relies on the strict alternation of odd and even threads. An extra warp end has to be threaded on shaft 2 to maintain this strict alternation. So essentially, a double sized block has seven ends rather than six ends to maintain this strict alternation of odd and even. A double sized block is threaded 1-2-1-2-1-2-1 where the red number indicates the extra warp end. A double sized block is seven warp ends. Block 2 is threaded 2-3-2-3-2-3-2; Block 3 is thread 3-4-3-4-3-4-3; and Block 4 is threaded 4-1-4-1-4-1-4. Single unit blocks are threaded with 3 warp ends per blocks as above. The actual threading for Draft II appears below.

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.

In Draft V, there are single, double, triple, and quadruple sized blocks. Following the example above, a single unit consists of 3 ends, a double sized block consists of 7 ends. A triple sized block for Block 1 is threaded 121 - 121 - 121. Notice that there are two places where shaft 1 is side by side … replace the hypens with a shaft 2, and the correct threading for a triple sized block is 121 2 121 2 121. A triple sized block will contain 11 warp ends, and can be increased by two ends to 13, or reduced by two ends to nine.

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.