How I Use My Sloper to Alter Patterns - 2 Back

Most experts on pattern alteration recommend altering the back first, but I always alter the front first. Why? Because it's harder for me. I find altering the back way easier, so I save it for my reward after finishing the front.

As with the front, start by analyzing the dart control. In this case, it's much simpler than the front: a single waist dart and it looks like the shoulder dart is rotated out in the yoke.
OK, here I compare the back yoke piece, already altered (see part 1) with a 3/4 inch narrow shoulder adjustment. I realize I need to make a narrow back adjustment. Look at the bottom of the photo: pattern in blue, sloper in red.
You can see the 1/2 inch I've removed from the center back.
Realizing I have not rotated out the back shoulder dart, I mark a line to separate out the back yoke.
Back yoke of sloper detached. Slash line to rotate out the dart marked in green.
I've rotated out the shoulder dart and trued the shoulder seam on the sloper.
Comparing the altered back yoke pattern (in blue) to the sloper yoke (in red), things are looking pretty good. The pattern is a little wider, but I've had my suspicions about my sloper, thinking it needs to be a tad wider at the back armhole. It's the rounded shoulder thing from doing too much work at the computer.
Comparing the altered back yoke to the main back pattern piece, I realize the same thing as I realized in the front - I need to carry the narrow shoulder adjustment down into the main back piece. Assessing how low the pattern armhole looks, I think I'll need to a petite armhole adjustment on the back too.
Just like in the front, I draw a box around the armhole with lines parallel and perpendicular to the grain.
3/4 inch narrow shoulder adjustment on the main back piece.
Marking the slash line for the petite armhole adjustment.
Petite armhole adjustment completed. It's smaller on the back than the front, about 1/4 inch. I'm getting concerned that the pattern armhole is still quite a bit lower than the sloper. Could it be that BWOF used a block with the shoulder dart rotated to the armhole and left unsewn? That is quite common, and I quite frankly hate it. You end up with all this slop in the back armhole. I'm sorry, but to me it's messy.
Had a thought. I made a larger petite armhole adjustment in the front than the back. Maybe it's time to walk the side seams and compare the length of the front to the back. They should match with this style. They don't.
After walking the seams from the waist up, I've marked a spot where the bottom of the front armhole should meet the bottom of the back armhole.
Using my curved dressmaker's ruler, I match the original curve of the back armhole.
Holding the curve at the top, I rotate it out to meet the mark where the front piece should match the back.
Armhole redrawn.
The big picture - comparing the pattern (in blue) to the sloper (in red). Observations: the waist dart is smaller, it will take up less fabric, but generally follows the lines of the sloper. Conclusion: leave it alone. Add a bit of width at the side seam for a bit more ease. Still worried about how much lower than the sloper the armhole is - leave it for the muslin - big question mark here.
Related damage - the collar pieces. I took 1/2 inch out of the center back, which affects the collar pieces. A good lesson to take is to remember that changes to one piece often affect one or more other pieces.

Thursday, in part 3, I'll discuss some more general issues involved in comparing slopers to patterns. Why not tomorrow, my loyal readers cry? Because tomorrow I'm going to the Moraga Library with my mother in law to hear a lecture on Faberge, Tiffany and Lalique, related to the new exhibit at the Legion of Honor in San Francisco. I've married into a good Russian family, and talks on Faberge are not to be ignored.

How I Use My Sloper to Alter Patterns - 1 Front

A member of PatternReview asked me to explain how I use my sloper to alter patterns. I can't 100% vouch for my method, as I'm totally self taught and not an accredited expert, but it certainly works for me.

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.

I selected Burda World of Fashion 1/2008 style # 125 because a/ BWOF patterns do not include seam allowances, so I could simply trace it, alter it and add seam allowances when ready to cut; and b/ the dart control is so obviously different from a sloper.

Start by analyzing the pattern's style. Try to determine where the dart control is located. In this case, it looks like the side dart is rotated into pleats that meet the yoke, while the waist dart is divided into two parallel tucks.
Here's the sloper with the yoke marked in blue. Cut the yoke away from the sloper, to compare with the pattern's yoke piece. I always start at the neck/shoulders and work my way down.
Here you see the pattern in blue compared to the sloper in red. Obviously, I need to make a narrow shoulder alteration.
The ruler tells me it's a 3/4 inch narrow shoulder adjustment.
I mark where I will slash the pattern (in green). Slashing is almost always either parallel or perpendicular to the grain, to preserve both style and grain lines.
Overlapping the pieces by 3/4 inch.
Because I made a narrow shoulder adjustment in the yoke, I need to carry it down into the front. Here I've marked (in red) a box around the armhole - one side parallel to the grain, and the other perpendicular. Apologies for the inconsistency of color - I worked on this over a few days as my neck issues permitted.
Using the ruler to overlap 3/4 inch.

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.

Assessing where the top of the pattern sits vis a vis the sloper, and also where the armhole is located (unfortunately not shown), I decide I need a petite armhole adjustment.
Drawing a line (in red) perpendicular to the grain where I will slash and overlap for the petite armhole adjustment.
Marking the sloper in preparation to rotate the side dart to the top pleats. I picked two spots each about a third in. I also marked points 1" above and 1" to each side of the bust apex. Finally, I drew a line from the top to each marked point and then angled in to the bust point.
I cut along the lines I just drew to, but not through the bust point. Tip: Reinforce the bust point with tape. I also cut through the midpoint of the side dart to, but not through, the bust point. Overlapping the black dart legs, which go all the way to the bust point, forces the top parallel darts to open.
Comparing the sloper (in red) to the pattern (in blue) at this point in the process and it's looking pretty good. I'm not sure about the top pleats - it looks like the pattern will take up less fabric than my sloper changes will indicate - but until I've gone through the whole process I'm unwilling to commit to any changes. It might be that the changes further down will change this dynamic, so I'll let them go for now. Judgment call - they do occur.
Now I'm going to tackle the parallel waist darts. On the sloper, I've slashed up to, but not through, the bust point at the waist dart. And then I overlapped the black dart legs, the ones that go all the way to the bust point but which would never be sewn that way. That forces the parallel pleats at the top to open wider.
After closing the waist dart, I drew in the parallel darts. Again, I picked two points on the waistline that seemed to approximate where the darts fall on the pattern. Then I picked out points that were 1" below and 1" to each side of the bust apex. Then I connected the dots from waist to points to bust apex.
I've slashed and spread the waistline parallel darts. Here you see the adjusted sloper over the pattern. I'm not sure what to think at this point. The pattern looks good compared to the sloper except for the top pleats/darts. I think I need to leave this issue for a muslin.
Here's the completed front piece altered. In a nutshell, I did a 3/4 inch narrow shoulder adjustment, a 3/4 inch petite armhole adjustment, and added about 1/4 inch at the sides. I'm leaving any other adjustments to a muslin.

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.