One of the key differences between Japanese Denim and majority of mass produced denim is the indigo dye. Brands like Momotaro and Kato use natural indigo/rope dyeing process which gives the fabric its deep blue color. Which is why I thought it would be good to share a few lines about the what’s the natural indigo dyeing process all about.

The process of natural indigo dyeing has existed in Japan since the end of Edo-Period. At that time, this was referred to as Real Indigo according to its high quality and rarity in Japan. Stepping into modern mass production required larger amounts of dye with lower cost, which eventually lead to invention of synthetic indigo dyeing and decrease in the use of natural indigo dye.

Artisans in Okayama still keep up with the traditional technique and the quest of achieving the original Japanese blue. Natural indigo dyeing material is extracted from harden prepared indigo plants called Sukumo which are liquefied by adding lime water,  it is then dyed up by the artisanal sense and experience which control the condition of dyeing material such as adding sugar or Japanese Sake to help the fermentation.

Majority of the jeans today are machine dyed using synthetic indigo. This method of dyeing leaves the dying material on a yarn’s surface, which is why the core part of yarn is still white. As a result, the indigo dyeing will fade from the fabric’s surface and provide the vertical fade of vintage jeans.

However, in hand dyeing the fabric is repeatedly dipped into indigo vat, indigo coloring is squeezed out, and dried up in the air. The process takes a long time as it is done by hands.  This is why, the yarn dyed by this method, is completely dyed even to the core part of yarn. Consequently, it makes less color fade in laundry and delivers deeper indigo blue color.