There are several ways to copy clothing.
1. Draft a pattern. This requires a skill set that is usually learned in a class or as an apprentice to a tailor. There are some good blogs on this topic and I am only just beginning to branch into this method.
2. Trace an exact copy of the garment. This can be done in a way that preserves the original garment by tracing it on paper, transferring all of the design element markings, darts, seam allowances, trims, pockets, button placement, zippers. This requires intermediate to advanced knowledge of garment construction and accuracy with tracing and transferring marks. I might write a how to on this sometime, but not today.
3. Deconstruct the original garment to get exact pieces for a pattern. This is what I am going to show you today.
Step 1: Tools and What you need to get started
1. Blue jeans you are willing to take apart. When I decide to deconstruct a garment it is something I do not plan to put back together.
2. A seam ripper.
3. Place to store the pieces as you remove them. A one gallon zip close plastic bag will keep pieces together.
4. Time. Don't try to hurry this process. You are studying the garment as you take it apart.
Step 2: Deconstruction Process
Examine the garment to find a seam that does not have another seam over the top of it. This is your starting point for removing pieces. With a pair of pants, or blue jeans this is probably the belt loops, then waistband. Find a starting point and carefully start cutting the stitches. Always work with your seam ripper moving away from you, careful not to cut yourself. If you get tired, stop and come back to it later.
Continue to remove seams, only on one half of the garment, always selecting the next seam that is not secured by another seam crossing over it. With blue jeans, the second seam is probably the hem, followed by the outer leg seam, then inner leg seam, center back, center front, zipper fly, any pocket, the yoke, then back pocket. If you do start a seam and find it is under another seam, move to the new seam, and work back to the point where the seams meet or overlap.
Areas that will require special attention are how the front pocket is made and how the zipper section is constructed. You can probably remove the zipper fly in a whole unit. Once the zipper unit has been removed from the garment, keep the whole zipper fly together. Use this when you sew the new garment to see how to re-create it. There are several ways to construct the fly. Just use the original for the pattern and sew the new one the same as the original. Same for the front pockets. Some pockets will have a facing, others will have a section that goes all the way to the zipper and is included in the center seam, others will fold-over. Last, take off the back pocket.
Keep all of the loose pieces together. Do not discard the section of the original garment that you do not take apart. This is your reference to sew the new garment. Keep your notes with the loose pieces. You will refer to them as you sew the new garment.
Step 3: What you need to buy and how to lay it out.
1. When you are ready to make your new copy of the blue jeans you deconstructed select fabric that has a similar drape and stretch as the original jeans. In other words, if they were stretchy try to find fabric with the same amount of stretch or give as the original fabric.
2. Make sure you buy enough fabric for the new garmet. In this case, Denim is sold in fabric stores by the yard. The bolt (what they call a length of fabric rolled around a cardboard core) will probably be available in either 44-45" width or 54-60" widths. If you want it to have a little stretch, look for denim with about 3% lycra. If you do not want much stretch look for 100% cotton denim.
3. To determine aproximately how much fabric you will need, lay out your pieces in an area not quite as wide as the fabric you plan to buy. If you know your fabric will be 60" wide, make sure you lay out your pieces in an area that does not get any wider than 28". This is because your fabric is folded lengthwise and you do not want to use the selvege (finished edge of fabric that runs the full length of the fabric).
4. You will need one front, one back, one back pocket, one waistband, the zipper placket, any yoke pieces and front pockets as well as belt loops and pocket linings for the front. You will actually need two of each, but the one deconstructed half will give you all of these pieces and you will have two because remember your fabric is folded.
5. Once the pieces are laid out within the narrow area 22" for 44"wide fabric or 28" for 60" fabric, measure the distance from the start to the finish and add about one third yard (12") to one half yard (18") to be sure you have allowed enough fabric. Divide the number of inches by 36, this will give you the number of yards you need to buy. This will probably not be an even number, it will probably be something like two or three yards and the remainder is the number of inches.
6. Now you can go shopping. You will need to buy as much fabric as you just measured out in step 5. You will also need enough thread to sew it and a few other things. Here is a list.
b. Denim fabric, the amount you measured and figured out in step 5
c. Jean needles to fit your machine. Don't skimp, you will be asking your machine to work on a tough fabric and a sharp needle will make the process much easier. (If your needle gets dull, change it. If it breaks or breaks thread you may need to get another size or change the kind of thread so go slow and be patient.)
d. A cotton calico fabric to line your pockets, not much maybe a quarter to third of a yard.
e. Interfacing for the waistband and maybe for the zipper placket. Ask your sales person at the fabric store, they know how to recomend these things for the fabic you picked out if you are not sure what you need. They probably sew a lot and will know how to figure out what you need. You will not need a lot, but interfacing is not very wide so you may need the full length of your waist. You will cut a narrow strip the width of your waist band and have more left over than you will use in this project. Keep it you may need it for the next pair.
f. A jeans button or snap this will be in the notions row
g. A jeans zipper. This will be with the zippers which are probably near the thread. Don't let the selection intemidate you. You are looking for a zipper that matches the color of the denim you picked out and it will be about a seven inch metal toothed zipper that says Jeans Zipper.
h. Matching thread and if you want, Jeans contrast thread, usualy a heavy cotton gold thread. Yes they sell this at the fabric store too, it will be in a sub section of the thread.
I. Optional items are rivits to reinforce areas where the pockets attach, but if this is your first pair of jeans skip it. You can learn how to do that later or you may never ever want the rivits, but if you do, it will be in the notions.
7. Pre-wash your fabric. Wash the calico and the denim just like you would if it was already made up. This helps the fabric to shrink before you sew it so the fit will be more accurate. You can wash them several times but I usually only wash it once. You may want to zig zag stitch the cut edges to prevent fraying before you throw them into the washer and dryer. DO NOT PRE-WASH THE INTERFACING.
8. Once your fabric has dried fold it length-wise and lay the pieces out like when you measured how much fabric you needed. Here are a few pointers.
b. Make sure none of your pieces overlap
c. You will probalby have the best looking garmet if you keep the top of the garmet pieces all facing the same way. By this I mean I would lay it out so that the top of the pocket, the top of the pants pieces and the top of the yoke pieces all start on the same side from the cross cut edges. This is just in case your fabric has a knapp (looks different when viewed from one direction or another) Velvets, velours and some dressy fabrics have this problem, denim not so much but just in case I still work from one direction.
d. The waist band can be placed either lengthwise or widthwise but look best length-wise.
9. Pin the pieces once properly placed. Check again to be sure you have all pieces placed before you cut in case you missed something and need to re-arrange anything.
10. Carefully cut the new denim.
Now you are ready to sew your new jeans.
Step 4: Sewing tips for your new jeans
I don't know exactly how your garment was constructed so I will give you the probable order for reconstruction, but you will have to refer to the pieces you have removed and the half that you kep for reference.
1. Make the zipper placket, set aside.
2. Make your front pockets.
3. Sew a long thin strip to use for cutting belt loops, cut belt loops to size and set aside.
4. Sew the front pockets to the front pant legs.
5. Attach the zipper placket and sew the front seam. The front seam is the portion under the zipper to the crotch, probably only a few inches long.
6. Make your decorative stitches on the back pockets.
7. Turn in edges of the pocket, press and sew.
8. Sew the back pockets to the back of the pants.
9. Sew each back yoke portion to the back pant leg portion.
10. Sew the back seam, this is the seam from the waist to the crotch. Where the yoke meets the pants section will be thicker go slow and have a sharp needle, this will be one of the thickest seam sections.
11. Sew the outer leg seams. Where the front pockets attach will be thicker go slow.
12. Sew the inseam. Matching the seams at the crotch. This is the longest seam you will make and where all the fabrics meet at the mid crotch go slow. Go slow and make sure your needle is sharp. You may need to press and even hammer the fabric to compress it a bit before you sew.
13. Place belt loops.
14. Attach waist band.
15. Fold up belt loops attach.
16. Top stitch the waist band.
17. Attach the jeans button and make button hole in waist band.
19. Wear your amazing new best jeans you ever had in the world and brag about it.
20. Now that you know it is not so hard, keep the original pieces for your next pair, repeat as desired.
Step 5: Sewing Terms and Definitions
Seam ripper - a sharp blade, manufactured to fit between seams and cut threads, leaving the fabric intact.
Selvege - the factory finished edge of fabric.
Yoke - the upper back between the waist band and the back pant legs.
Zipper Fly or Zipper Placket - same thing. The whole unit that contains the zipper, it is usually three pieces sewn together as one unit but can just be folded - not all garments are exactly alike.
If I have other terms here that I forgot to add, send a message and I will update the sewing terms and definitions.
You can also view my blog at www.sew-i-do.blogspot.com
or for my blogs on jeans specifically:
http://www.sew-i-do.blogspot.com/2012_04_01_archive.html and http://www.sew-i-do.blogspot.com/2012_03_01_archive.html