Case Study | PBJ "Greencast Indigo" Denim review by Ali Mirza


Note: This is not sponsored content, and the jeans were purchased from the site at retail price.

After doing write-ups for naturally colored cotton, luxury Suvin Gold, recreations of the oldest jeans from the 1800’s, persimmon dyeing, incredible Aizome, and limited edition extreme heavyweight Samurai’s I thought it would be suitable to look at innovations and perfecting the most basic denim staple: slim-straight, mid-weight jeans. 

I knew which brand I wanted to go to do this because, in my humble opinion, nobody has perfected the construction of modern jeans like Pure Blue Japan. In all the pairs I have seen, the choice of thread, the tension of the sewing, and having a comfortable cut is something that Pure Blue Japan just does perfect. Despite the fabric having so much character and the cut being so good, the jeans just feel incredibly comfortable. There is just the right amount of breathing room where needed whilst adding a great silhouette—it’s a master stroke of denim design in my opinion. Anyway, back to the construction after a bit more about the fabric. 

  • The fabric is at home in cold weather but the color looks wonderful in icy environments too.

Fabric - Color

It’s hard to start with these jeans without talking about color and hue. This Greencast indigo dyed fabric is insane. In the past, my favorite hue is when indigo has faded and hits that ocean mid-blue electric color. These jeans start off there but turned up to 11. There is always an iridescent aura surrounding the fabric color and when the sunlight hits it right it shines in such a lovely way. It’s not a shiny color, but the hue has a lightness about it that’s just understated enough to work as a pair of workwear jeans and yet a unique brightness that makes it obvious this dye is something else. Pure Blue Japan states they mixed indigo and green dyes (sulphur, I believe) many times trying to get the right shade. I can believe that it must have taken numerous attempts to get this right as it is stunning.

The iridescence reminds me at times of rivers or lakes near glaciers that can glow iridescent blue because of the presence of rock flour. The blue has a cold, radiant, yet fresh look to it—you could equally call these glacier jeans (these are the closest photos I have, Google "glacial rock flour" for even better matches)!

American, Australian, Recycled Cotton & Weaving:

The color of course, is reliant on having the right blend of cottons and texture to interlace with. In this case, Pure Blue Japan uses a blend of American and Australian cotton with 30% of the American/Australian cotton being recycled, picked up from the result of the spinning process.

Australian cotton is famously clean of debris whilst also having a coarser hand-feel. American cotton is similarly clean but just a touch finer and stronger. The threads here have a characteristic slub, a certain plumpness, and the recycled cotton gives it that additional textured hand feel yet soft on the body. This is a very characterful thread that’s supple, thick, and has plenty of texture—something that the weaving process can take advantage of and further highlight.

Accordingly, these slubby threads are then woven on a Toyoda loom under lower tension but not too low. The reason for this is "a bit of a balancing act" as Pure Blue Japan puts it. When the tension is put very low the slubbiness and unevenness does increase, but the density of the weft threads decreases which if pushed too far leads to a fabric that feels less like denim. So, to have a fabric that has the right stiffness and tenseness but also the right slubbiness and unevenness, is like walking a tight-rope—too far in either direction can lead to losing one of these lovely characteristic features. 

Interestingly, this balance can also shift as the seasons change, as during the rainy season the fabric becomes softer while in the dry season you find a stiffer fabric. An important question arises here as Pure Blue Japan points out: do you try and counteract this change during the season, or do you allow nature to leave its imprint on the fabric as the seasons change? The four season nature of Japan seems to imprint its characteristics on Pure Blue Japan’s philosophy of weaving! The end result of this effort is a 14oz. fabric that has deep character on a textural level with suppleness, stiffness, slubbiness, unevenness all highlighted in full on a tactile level. Then visually the color takes a highlighter and points out all of these features yet again. The fabric itself is just flat out an incredible piece of art.


Such a gorgeous fabric should be paired with careful, detailed, and well-though out construction. And here, Pure Blue Japan has knocked it out of the park. I want to start with talking about the main chainstitching used and then the very thick finishing stitches used on the pockets and crotch, and finally the other details like rivets, button-holes, buttons, and leather patch. 

First, I should point out one of the features I look closest at it how the stitching threads interact with the base fabric aesthetically and functionally. It might help to start off with how not to do it:

In other clothes that are not so well thought out, you can tell that the manufacturer simply picked whatever thread was available and combined with whatever fabric was determined by the designer. For instance, I have seen jeans with a textured, natural cotton fabric with a soft-dullness combined with stiff, shiny, slippery polyester stitching; the stitching floats free of the fabric and doesn’t integrate with it, the seams seem stiff and hard. 

On the other hand, if I had to show somebody what the perfectly thought out stitching and seams look like on a pair of modern jeans, Pure Blue Japan would be first, second, and third on that list. The chain-stitching has a softness and even fluffiness to it and the seams feel supple, the fact that the seams undulate containing extra fabric means that the fabric is not pulled taught and under tension but is gently connected. Pure Blue Japan’s tend to be very comfortable when sized right and I’m becoming convinced that these thick threads and what seems like lower tension seams are part of the what makes them just feel so. . . right. Even when the threads are such a different color like in these GRE’s the texture fits perfectly. It is so obvious that so much time went into picking the right threads, testing out the right tension on the sewing machine, and determining how to fold the seams appropriately. 

And this is part of detailing that usually isn’t considered when reviewing jeans. The amount of time PBJ spends getting just one stitch correctly makes them extremely detail-oriented but this might not be noticed explicitly unless one combs over every inch of the jeans. We can see this again in what is my favorite bit of sewing on any jeans. The pocket bags and the crotch.

The lock stitch on the pocket bags is usually reversed back for security or left as is, in the PBJ’s every pair I’ve seen has what looks to be a hand-tied knot. On the crotch, rather than the usual bar-tack, the same chunky thread is used to tie everything together and the last stitch used to cover over the first one. Again, this is something unique to PBJ as far as I can tell, involves spreading out the securing of the crotch over a larger area rather than a single bar-tack. These are the thickest, strongest, fluffiest threads I’ve seen on a pair of jeans at this weight. 

The stitching color is also perfectly paired with the color of the fabric. Rather than the usual indigo button holes, these have the orange threads used for the button holes. The stitching here on the pocket bags, and the yellow inseam accentuates, and is enhanced all the more by the Greencast Indigo. The rivets are not gun metal but a bright copper color that again looks great with leather belts of all kind. 

Speaking of leather, the patch on the bag is a beautifully textured sheep or deerskin with PBJ’s standard print. The buttons are steel and even here the details are stunning. The inside portion of the button shows a copper coated with black that contrasts with the steel beautifully. To top it all off is the indigo leaf embroidery requisite in every PBJ pair. 


The most detailed well-thought out stitching; a fabric that cuts right across the slub, stiff, uneven, supple, rigid category; a cut that to me, looks fantastic, and yet is so comfortable you don’t even realize you are wearing it. The fabric is light enough to wear for most summer days and I’ve worn it below freezing and felt fine. The color is unique, iridescent, but most of all just gorgeous. It’s a pair of jeans I could easily dress up or use as workwear. Pure Blue Japan’s GRE-013 is a sort of greatest hits of the defining features that make a great pair of jeans great, but now combined into a single pair.

The strength of American cotton combined with the coarser nature of Australian cotton and the texture imparted by the spinning and inclusion of 30% recycled fibers, gives a base that is already textured even before PBJ runs their magic balance of tension and slubbiness on looms partly imprinted by seasonal changes.

10/10 effort by Pure Blue Japan and, even more surprisingly, 10/10 execution. For the kind of jeans the GRE-013 tries to be, I can largely find no qualms. This is the definitive modern workwear, versatile denim for those looking for a synthetic indigo lighter than is usual. I cannot wait to see these with a patina in a few years! 

Many thanks to Ali for taking the time to put together this incredible review.