After knowing the basic terms,the types of needles,I think it would not be fair if I didn't pay attention to threads!!
I know it does not sound as glamorous as researching types of gussets or adding zips( we will get there too in time),but imagine you are in a supermarket & suddenly you find your bag leaving a trail of everything you just bought through the big hole in the bottom of your bag!!!
Actually I am picturing it right now & am finding it pretty hilarious........I am imagining what all will be there in your bag........OK yes,I am visualizing naughty things;)
But hey..............its your fault ,you did not choose the right thread, if you had your bag wouldn't have given up on you!
So now that I have proved beyond a shadow of doubt that you need to choose your thread as wisely as you would the needle,here are the different types of threads which we commonly use.
COTTON:Cotton thread is in my experience the most common thread used worldwide because of the thread's strength, durability and ease of use. It leads to a well-defined line of machine stitches.Cotton threads are available in a wide range of colors, and are used for sewing on light and medium weight cottons, rayons and linens. Cotton thread is also mercerized, it is a finishing process that makes it smooth and lustrous, also helping it to take dye better.The cotton threads come in medium thickness (yup,threads too have sizes for their thickness & you thought only you had a waist size to boast;)
100 PERCENT SILK-Silk thread can be chosen for its gorgeous sheen. It is one of the most trouble-free threads to use for machine sewing. Strong and durable, it does not stretch & adds a marvelous sheen to your sewing.I use it very regularly:) Its fineness makes it ideal for basting all fabric types, as it does not leave holes from stitching or imprints after pressing.
POLYESTER: It is a general purpose thread ( medium-weight ) used for the majority of projects that can be sewn by a sewing machine. With a large variety of colors and spool sizes, general-purpose thread is ideal for use with most fabrics. Most polyester threads have a wax or silicone finish to help them slip through the fabric with a minimum of friction.
I am adding a pic to compare a thin cotton thread & medium weight polyester thread ,see the difference in thickness & imagine the difference the threads will make to the strength of your bag's seam!