DENIM FABRIC BUYING GUIDE

Denims range in weight from about 6oz through to about 15oz.   

• 6oz denim is similar to a heavy weight chambray and great for shirts, dresses and shorts
• 9oz denim is normally the starting weight for jeans.  This is a very versatile weight as it is light enough for structured dresses and skirts, but also heavy enough for light weight jeans.   
• 11oz - 12oz denim is probably what you are used to seeing in the stores for your 'average' pair of jeans.  
• 13oz denim is thick and sturdy denim, a great option for hardwearing jeans and bags.   
• 15oz denim is really thick! 

The denim you choose will either be rigid denim or stretch denim - you will need to refer to your pattern for what type you will need.  As the names suggest, rigid denim is just that  - normally 100% cotton.  While stretch denim will have a lycra/elastane/spandex content.   The percentage content of the spandex and the percentage stretch are the two main things to look out for when selecting stretch denim.   Don't get confused between the two!   Your pattern will have been designed with either a stretch content or stretch percentage - so pay attention!  

• STRETCH CONTENT:  This refers to the amount of lycra/elastane/spandex yarns used in the weaving of the denim.  Normally this will be somewhere between 1% and 4%.  
• STRETCH PERCENTAGE:  This refers how far the denim fabric will stretch across the grain, or from selvedge to selvedge.   You can easily calculate this at home by taking a 10cm square piece of fabric and stretching it across the grain as far as you can.  For example, if you can stretch your 10cm piece out to 14cm, then the fabric has 40% stretch:  ((14cm-10cm)/10cm) x 100

When denim is manufactured at the mill it is first woven on looms, then often undergoes a treatment process called sanforizing.  This process is essentially moistening, steaming and stretching the fabric repeatedly to   remove most (if not all potential shrinkage).   The result is often a smoother looking denim.  

Loomstate, or raw denim, on the other hand, doesn't go through the shrinking process.   We end up with denim fabric that is straight off the loom.   This gives a slightly rougher, more textured denim.   If you are using this denim be sure to take into account that the fabric will shrink when washed - normally 5-10%.    Some people prefer the slightly more rugged look of this denim and choose to wear the denim without washing it first.  If you choose this option - consider sizing up and your garment will shrink to fit after its first wash. 

Selvedge denim is denim fabric that has tightly woven edges (that don't fray) on either side of the fabric.  The selvedge is normally a contrasting colour(s) and often used as a design detail in the finished garment.   Selvedge denim is woven on narrow looms, where a continuous weft yarn snakes left to right and back again across the fabric.   This continuous weft is what creates the finished edge.     Non-selvedge denim by comparison has the weft yarn cut each time it reaches the edge of the loom, creating a frayed edge.  

The important consideration when choosing between the two is to note the width of the fabric.   You are likely to need more of a narrow selvedge denim which is often 70-80cm wide.    If you are using selvedge denim to make jeans, you'd lay the pattern pieces out so that the outer leg seam sits on the selvedge, giving a great design detail when you turn up your cuffs. 

You can choose to either prewash your denim or not before sewing.  Except for the raw denims you are not likely to experience any shrinkage.  BUT - I do recommend you check shrinkage first, and take this into account when sizing you garment.    A quick way to check how much your chosen denim fabric might shrink is to cut a swatch (approximately the size of a post card), record its size, soak it thoroughly then dry with a hot iron.   Compare the swatch size before and after.    From here you can decide if you want to pre-wash or not. 

If you do choose to pre-wash your denim fabric, consider the following:

• Place the denim loosely in the washing machine.  You are almost always guaranteed to get dye leach from your denim - this leaching contributes to the wonderful and unique patina of your ol' trusty worn jeans.   If your denim is too cramped in the machine, the dye may leach unevenly leaving permanent marks where you probably don't want them. 
• Consider washing the denim in small batches.   You could cut your denim fabric into smaller pieces to ensure a loose fit in the washing machine.   Check against your pattern pieces first to ensure you will still be able to cut them all out!
• Use the bath tub!  If your machine just won't handle the bulk of a large piece of denim - simply soak in the bath tub instead.  Make sure you leave the denim for some time to really soak through.  
• Use a wash temperature and cycle as you would wash your finished garment.
• Iron when dry.  Use the iron setting that you will use during construction or what you will iron the finished garment with - whichever is the hottest.