#burn test

We get this question often, and the short answer is:  burn it to be sure. But that answer is a bit too short when we’re talking about assessing vintage Japanese kimono silks.  

Yes, the smell of burnt silk is distinctive - similar to burning hair - but vintage kimono fabrics can often be a blend of silk with linen, cotton, wool, or synthetics, which sometimes makes it difficult to be 100% sure of the fiber content.  The video below shows the difference between burning silk and polyester which are often difficult for folks to differentiate.

The video below shows the difference in burning and ash between many more fibers, but has no audio, which is a little disappointing.  Still, it’s a useful demonstration.

At Kyoto Kimono, we’ve been selling vintage Japanese textiles for over 20 years, and it still surprises us at times to see that what we thought was 100% silk was only a blend or was even fully synthetic.  

Polyester was a popular substitute for kimono silks after WWII because it was cheaper to produce but could offer the look and feel of traditional silks.  Kimono made before WWII are likely to be made from natural fibers, but that could still mean a blend of silk with cotton, rayon, wool, or linen.   

Finding a place to snip some of your kimono fabric can be a challenge.  Most kimono are lined and hand-sewn with salvages hidden inside the seams, so getting to an edge to snip and test is impossible without opening up some stitching. (Some unlined kimono may have salvage edges exposed, but many will have the salvage edges folded under and sewn shut. Summer cotton kimono are the exception, where the fabric edges are usually exposed.)

random stranger: thanks I just got it! it's soft and woolly

me: it looks it! can I test?

them: yeah go for it. they hold out their sleeve

It has been a bit since I posted anything original in a while. I have been busy with real life and ✨️planning projects✨️

In efforts to plot the next few steps of my current project, I have a fiber content question.

I purchased some mystery fiber from my Guild today, and this one treasure (out of many) is amazing and has a stunning color. I'm going to make a shawl out of it and sell it through my Guild's program this winter.

But what is the fiber content? I did a burn test and have some notes, so hopefully, somebody with more experience can point me in the right direction here!

This is the fiber. I now have 6 cakes, weighing something like 800-900 grams total. I haven't broken out the scale or figured out yardage yet.

I cut off a sample and burned it, then realized it was NOT the results I was expecting.

It lit up quick with a bright yellow flame, and the first time, I startled and dropped it in the dish. The second time (pictured) I was prepared but had a much shorter sample this time. The two pictures are about one second apart.

When burning in the dish, the flame diminished pretty quickly but continued to smolder down the length. The thicker part of the yarn didn't burn all the way and self extinguished. It smelled somewhere between paper and a slightly green wood but didn't produce any noticeable smoke.

The ash is very fine, but smeared the dish with a little grease when I picked it up. (As seen in picture two above) The part that didn't turn to ash did crumble a bit in the fingers with a little pressure but is still recognizable as fiber. It is very soft ash, with no lumps.

I think this is cotton! But if I'm going to sell it, I want to be a little more sure than "yeah, it's a plant fiber and cotton is the first one people think of".

The Burn Test

Different types of fiber burn differently. Cellulose, animal and synthetic fiber all respond differently to flame, and analyzing how they respond to flame (from speed to smell and type of ash) will help you identify the specific type of fiber. This is important information to help you determine what specific dye will work best on each particular fabric.

We will use "change magic" to form ourselves into 3 groups of 2 or 3 people to work together to identify a series of fabrics and determine whether they should be dyed with fiber reactive dyes, acid dyes, or not use dye at all, instead coloring via surface treatments like paint.

Preparation and Supplies

A flame source. We will use a lighter.

Tweezers. Some fabrics can burn unexpectedly quickly, and tweezers ensure your fingers stay safe from the flames.

A fireproof dish. Dropping flaming fabric onto a flammable surface – or even worse, your fabric stash – could spell disaster. Always use a fireproof dish under your burn testing area.

A glass of water. Just for extra safety, I like to keep a glass of water nearby to extinguish any flames in the case they get out of control.

A ventilated area. Burn tests should be done in a space with plenty of ventilation. We will use our exhaust fan during our burn testing exercise.

Burn Test Chart, which will help you identify your fabric. We will have copies available in class, and a digital version of the burn chart is also available for you on canvas.

Your fabric swatches! You’ll each receive a series of fabric scraps to use for your burn tests as well as a log to record your observations.

The Burn Test

Hold your lighter in one hand and your fabric in tweezers in the other hand. As you bring the fabric and the flame together, note how the fabric reacts, how the flames burn and what the ashes are like. These components of the test all provide great insights into the identity of the fabric.

Some questions to consider:

Does the fabric curl away from the flame? Does the fabric catch immediately, or take a while to light? Are the flames bright? Is it burning quickly, or does it smolder out? Does the fabric simply melt as the flames sputter along? What smell does the smoke give off? What shape are the ashes? Do they fall apart when you touch them, or do they stay hard? Are they congealed onto the fabric?

Please be careful when examining the ashes, as they may still be hot or contain embers.

Use the burn test log sheets distributed during class to collect your burned fabric sample and observations described above. Use the burn chart to do your best to identify the type of fabric you have tested. Scan or take a picture of the completed sheets and post to your blogs to receive credit for your research. This will be graded as part of your blogcheck #1 grade.

Images above:

It is interesting to go look back and realize how old these pictures are.