This topic came up recently on the USITT Costumers e-list, and i had just been studying it for another of the textiles courses i've been taking at the NCSU College of Textiles. I thought i'd repost my response and elaborate on it a bit more here, to create a public googlable resource as well.
Essentially, someone asked how to quickly remove the heavy-duty crisp OMG NEW! sizing that you find in some modern textiles, whether there was some speedier process than "wash and wear the item 3098520985 times." She wanted to soften the hand of the fabrics for the purposes of making a costume that's supposed to look lived-in and not crisp-tastic. This is a fairly common issue in the field, when you have new fabric or a new garment, but a character whose clothes are supposed to be well-worn. It can also be a big issue for dyers, as fabrics with sizing in them will often dye irregularly or with undesirable gradations and uptake levels. Hence this post!
Basically, there is not just one type of sizing. Different fabrics, fibers, and weave structures require different types of sizing. A process which removes one type of sizing efficiently may not have as good of an effect on another type of sizing.
A lot of modern fabrics are sized with PVA (aka PVOH or polyvinyl alcohol, which is basically white glue). It's technically water-soluble, but can take multiple standard domestic launderings to totally come out. If PVA sizing is particularly tenacious, adding a very small amount of sodium hydroxide (NaOH)--aka lye or caustic soda--to your laundry load will help with removing it faster, but it can also act as a breakdown agent, which in fact might be desirable if you want the fabric(s) to look old, faded/distressed, etc.
Lye is highly corrosive and easily splashed in liquid form, so be sure to use gloves, splashproof goggles, and great care when working with it, rather than just dumping some into the machine carelessly.
In fact, it'll be a lot safer (and probably easier to purchase, handle, and store) if you use lye soap flakes instead of NaOH solution. Also, maximum agitation and higher heat of the wash bath (above 75F/25C) will help, too. If you have some particularly tenacious PVA sizing, you can even boil the fabric to get it out.
Two other common sizing agents used are a compound called CMC and traditional starch.
If your fabric is sized with CMC (which stands for carboxymethylcellulose), that's the easiest to remove--just running a hot laundry load will usually do it. If you have soda ash or washing soda on-hand for dyeshop purposes, tossing a little into the bath will desize CMC from a fabric even more efficiently.
Traditional starch is actually often the most difficult to fully remove. Like PVA, it requires high heat and agitation, and will come out quickest if you boost the laundry bath with the enzyme amylase, which is found in some enzymatic cleaners. Detergents with amylase don't always feature the word "enzymatic" in their ad copy, so it pays to read the labels. Often ones that cater to the Green market share will have it as a component--Seventh Generation and Nature's Miracle, etc. (Amylase is also found in saliva, but your coworkers might look askance if you go ask everyone in the company to come spit in your washing machine.) Peroxide bleach will also remove starch, but also tends to weaken cotton and linen fibers so use care if you go that route.
How do you know what something is sized with?
Unfortunately, there's no way to really find out unless it's printed on the tag or bolt end or whatever. Here are a few tips to help with your guesswork though.
- Starch is typically only used in cotton processing, so if you have a non-cotton fiber, it's unlikely to be sized with starch.
- Cotton doesn't automatically mean "starch" though--it could be PVA or CMC.
- Nylon fabric is often sized with an acrylic sizing, which can be removed with a cold or warm (not hot) cycle and lye soap.
- Polyesters are usually sized with water-dispersable synthetic sizes which are susceptible to lye soap.
In general, when i'm desizing fabric to prepare it for dyeing, i start with a hot laundry cycle, high agitation, and using an enzymatic detergent plus washing soda. If it's still stiff after that, then i start troubleshooting with other methods.
Also, on a totally unrelated note, my former employer, the LA Opera, is hosting the first costume sale in their history this weekend, October 10th. If you are in the southern California area, i HIGHLY recommend going to check it out. The LA Opera produces top-quality costumes for internationally-renowned performers so this really is a one-of-a-kind opportunity. You can download the press release with all the details here: http://www.laopera.com/press/release.0910.aspx
Tags: ask labricoleuse, dyeing
