I'll start by explaining some terminology. Many sewists have drafted a moulage, which is a very basic top with side and waist darts that has absolutely no wearing ease at all. It fits like a second skin, and in fact is what I used to cover my adjusted dress form. A sloper is also a very basic top, but it has minimal wearing ease added. If you sewed it in real fabric, it would be wearable, though pretty boring. It has no style details. Some people also refer to a sloper as a block, but to my mind that is incorrect. To me, a block is a basic pattern that has some style details. For example, I drafted an armhole princess seam top, a shoulder princess seam top, and a basic shirt with collar, using my sloper as a starting point - these are my blocks. If I'm altering a shoulder princess pattern, I'll compare it to my shoulder princess block.
To begin the process of comparing a commercially published pattern to a sloper, here's what you need to have on hand:
- a clean traced copy of your sloper, front and back
- a copy of the pattern, with the stitching lines marked. Most patterns do not show the stitching line, only the cutting line, so you need to refer to the instructions to determine the seam allowances and then draw them in
- extra tissue or tracing paper
- a ruler. I prefer to use a 24" clear quilter's ruler.
- a curved dressmaker's ruler
- pencils or pens. I usually use a .5 mm drafting pencil, but for the examples below I used colored Sharpies. I prefer the drafting pencil since I can erase and it also doesn't smear, but the colors definitely show up better in the photos.
- Either removable tape or pins. My cutting mat is hard, so I use the tape, but if you have a cardboard mat, pins work better.
Note for the next few pictures I have matched up the center front and waist of the pattern to the sloper. Remember, the center front of this pattern is NOT on piece 1, it is actually on the button placket. Something to keep in mind when altering - determine where the actual center front is located.
I'm about halfway through my process - although I have to tell you, I rarely go to this level of detail any more. Once I figured out my "usual" alterations, which took about five tops going through this process, I didn't need to go to this level of detail anymore. I pretty much just do my standard alterations - narrow shoulder, petite armhole, add a bit to the side seams - and if it's a really different pattern in terms of dart control I'll sew a quick & dirty muslin.
Part 2, the Back, will be tomorrow.