How To Draft A Basic Conical Block (Torso Only)
This tutorial shows how to create a conical corset block for the center of the torso. It does not include shoulder straps. This block is the basis of all conical corset and stay patterns that I draft. It is not, in and of itself, a working pattern. It shows one solid half of the torso (center front to center back), and has no seam allowances. This method of making a basic block will work for most body types, with the notable exception of cases where the finished waist measurement is greater than the wearer’s natural modified bust measurement (the modified bust measurement will be explained shortly).
Some basic math skills are required. You must be able to add, subtract, multiply, and divide. There is no getting around it short of creating complex shortcut charts which I have no interest in creating. If you have a basic calculator and can follow the directions to create your measurement chart, you should be fine even if you are math-phobic.
Some basic variations of the block shape will be given at the end of the tutorial. This block does not include a high back or shoulder straps. Those details will be illustrated in a separate tutorial, but should be included in the basic block when desired in the final pattern.
Needed Tools
I do not have computer programs for pattern drafting, so I do all my drafting the old-fashioned way, by hand. Fancy tools are not necessary. You will need some sort of large paper or pattern drafting paper (it might be hard to find, but very cool, as it has the inches or centimeters marked on it already). I use a roll of butcher paper on a large cardboard cutting board. You need a pencil, eraser, ruler (I like clear “quilting” rulers), flexible ruler (available at some art stores and college/engineering supply bookstores), a basic calculator, scratch paper, and the measurements of the person being fitted for the block.
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Needed Measurements
Measurement instructions can be found on my Measurements page, under “Standard Measurements”.
The needed circumference measurements are the Bust, Underbust, and Natural Waist. You also need the vertical distances from the underbust to the bust, and the underbust to the natural waist. I am making this block from my own measurements. In the image below, the unaltered measurements are to the left. The distances are on the right (with the “to” in front of them).
The “Mod” column shows the modified measurements. For the waist I am drafting for a reduction of 3”, so the modified waist measurement is 29.25-3=26.25. The bust modifier is based on the bust measurement minus the underbust measurement, and then divided by 6. That is, (36-30.5)/6=0.91. Written another way, that is 36-30.5=5.5 and 5.5/6=.091. .091” is an awkward number to work with, so I round it up to 1” for the modifier. Round to the nearest ¼” if you are working in inches, or the nearest .5 centimeter if you are working in metric.
The ½ column shows ½ the underbust measurement and ½ the modified waist measurement (the circumference of half the torso). The ¼ column shows ¼ the underbust measurement and ¼ the modified waist measurement (approximately the circumference of the back quarter of the torso).
If you are markedly asymmetrical, you will need to take additional measurements, rather than approximating using math. I would recommend making a separate chart for each half of your body. Use measurements taken on each half (or each quarter if needed) of the body separately. Be sure to take circumference measurements for your entire torso to check the accuracy of your half measurements. Both halves should add up to the whole measurements. When the working measurements are half circumference, the bust modifier is based on a division of 3 (rather than 6).
Making the Basic Block
Start by making a long vertical line that will sit at the underarm. This is your centerline. Use the vertical distance measurements to mark the locations of the bust, underbust, and waist.
Mark the top edge of the corset at the underarm relative to the bust height. Usually ½” works well. If the wearer has a particularly short torso (roughly 6” or less total distance from the bust to the natural waist), the top of the underarm can be as low as the bust mark. If the wearer has a particularly long torso, it can be placed higher without causing discomfort at the underarm. If you wish, you can take an additional vertical measurement for the highest comfortable underarm location, and use that direct measurement instead of approximating.
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Mark horizontally at the bust height. Width does not matter at this stage, as long as it extends past the final width dimensions of the block.
Use the ¼ column underbust measurement. Measure towards the back from the centerline at the underbust height and make a mark.
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Use the ¼ column waist measurement. Measure towards the back from the centerline at the waist height and make a mark.
Draw a line between and extending beyond the two new marks. This is the approximate back side of the block.
Draw a line horizontally at the waist height.
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Mark the waistline at ½ the distance from the centerline and the back edge.
Square the ruler on the back edge so it goes through the above mark. Draw a line.
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Use the flexible ruler to create an arch along the bent waistline. Verify that the distance is nearly identical to the ¼ waist measurement. If the back side line is on a steep slant, you may need to re-mark the ¼ waist measurement along the curved line and re-draw the back side.
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On the back side, start at the curved waistline and re-measure the underbust and bust heights. Mark them.
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Create a curved underbust line from the new underbust mark at the back side. Verify the length of the curve relative to the ¼ underbust measurement. Adjust it if needed.
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Now we move to the front half of the block. At the waist height, measure forward of the centerline to the ¼ waist measurement.
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At the bust height, measure forward of the centerline by the ¼ underbust measurement. Extend that line by the bust modifier. Make a mark.
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Draw a slanted line between and extending beyond the two new marks. This is the front side.
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Create a curved waistline as on the back quarter, squaring to the front side.
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Verify the length of the curve is the same as the ¼ waist measurement. Move the mark and re-draw the front side if needed. Steeper curves are more likely to need modification.
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Along the front side, measure the distance from the waistline to the bust height. Make a mark.
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Create a curved bustline from the new front side bustline mark to the center line. Verify the length is the ¼ underbust measure plus the bust modifier. Adjust the mark and front side if needed.
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Find the intersection of the straight bust height line and the front side. Square the ruler to the front side at that intersection, and draw a line back from the front side.
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Find half the total distance from the bust to the natural waist (in this case, ½ of 7.25, or 3.625, which rounds to 3.5). Extend the front side below the waist by this amount. Depending upon the individual, and the length of the torso below the natural waist, this extension can be significantly longer without discomfort or inconvenience. However, I have found that this amount of extension is comfortable on a majority of people. Alternatively, take a direct measurement of the front of the torso from the underbust to the lowest comfortable front centerpoint of the stays. Use that measurement instead of a mathematical approximation.
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Curve the bottom edge of the block from the centerline waist mark to the lowest front mark. The descent should start a short distance from the centerline, but should not become steep until it is half-way from the centerline to the front side. The meeting point for the angle used to create the curve in the waistline is at the half-way distance.
Another way to look at this curve is to divide the horizontal distance into thirds. The first third is a slow slope. The second third is a steep slope. The last third (which can appear to be less than 1/3 because of the angle of the front edge) is a slow slope, nearly perpendicular to the front edge.
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Next find the point where the top edge of the front half starts to curve into the armpit. This point is above the angled intersection of the waist line. In other words, if you draw a line parallel to the center line upwards from the point of the waistline angle, make a mark where the line crosses the top edge. Start the curve to the armpit from this point.
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This block does not include shoulder straps, so I want to keep the top of the back below the shoulder blades. Square the ruler to the back side at the horizontal bustline and draw a line.
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Smooth the top line from the back side to the armpit.
Darken the outline, and strongly mark the centerline. I recommend using a pen to make it permanent and easily visible underneath other paper. This is now a basic conical block.
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Block Variations
The block variations are drawn in pencil within the inked basic block.
This variation will cause the corset to hug the torso to the underbust, and then curve out to the bust. Create a curved underbust line and measure to the ¼ underbust measurement. Draw a new front line from the bottom front to the underbust, and then curve it out to the curved bust line.
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For a more scooped bust, start the top edge part-way between the curved bustline and the straight bustline. Increase the height of the top edge in front of the armpit. This will expose more bosom at the very center front and create a more dramatic sweeping line.
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To create more squish and upward thrust, bring in the top of the front side and extend the height by the same amount. If you bring in the front without increasing the height, it will just cause spillage. Do not bring the front edge all the way in to the ¼ underbust measurement.
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If you want a higher back, curve the top edge up approximately half-way from the centerline to the back edge along the bust line. Be careful that the height of the back is either low enough to be completely free of the shoulder blades, or high enough to cover them at all times. If the height is in-between those two, it will rub the bottom edge of the shoulder blades as the wearer moves.
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Making a Usable Pattern
The block pattern can be divided up according to the piecing patterns of just about any historic conical stays or bodies. Just divide up the space according to the pattern being imitated, and add seam allowances and other needed marks.
I currently have illustrations of converting a conical block to the following styles of stays or corsets:
