May 7, 2024
SEE UPDATES AT BOTTOM (July 17, 2025)
We had a lab metallurgically test the s5 blade we sent to Matt Jensen to find out why it bent and broke more easily than the ones sent to Shadiversity and The Steel Mindset, which came from the same batch. As a result of the investigation, we found out that at least one s7 blade was mixed into the batch of 70cm s5 Katana blades prior to heat treatment. This appears to be the result of a sorting mistake, which occurred in mid-2023.
The heat treatment for s5 used on s7 will yield a blade which is less hard and more likely to set a bend. It will also be less durable, as noted in Matt Jenson’s video. Cloudhammer previously tested the hardness of 25% of each run, so we estimate that up to 5% of that batch could be affected.
The models affected are the Black Lotus with the dark brass (but not black brass, which were mounted to a later batch), the Crane Sakura, and the Surging Dragon purchased from RVA Katana between July of 2023 and early Autumn of 2024.
If you bought one of these models during that time, and have noticed your edge has rolled on anything harder than fresh bamboo, or has set a bend, please let us know so we can send you a replacement.
Cloudhammer has since improved their sorting and organizational process, and now tests the hardness of each blade, so s5 swords made since mid-2024 should not be affected.
Cloudhammer apologizes for this mistake and the inconvenience it may have caused you.
UPDATE 1 (5/16/25): The blade tested by Joe at Steel Mindset also tested as s7 with an HRC of 50. Cloudhammer is currently reviewing it's manufacturing process from acquisition to production to QC.
UPDATE 2 (5/22/25): We have gotten reports from two customers that s5 katana purchased from the newest batch have rolled on green bamboo. We are having them sent back and we will hardness test.
Cloudhammer has been informed and will XRF test it's remaining blades on hand, and send in samples for EOS testing
UPDATE 3 (5/24/25): We decided to suspend sales of s5 until we can confirm the hardness and bend resistance of the stock on hand (this has all taken place when I've been on a family vacation, and I'm not in the shop to do this), and asked Cloudhammer to test the s5 blades they have on hand.
The used XRF testing (not as accurate as EOS testing, which is what the US testing company used), and there was some s7, as well as two which fit the profile of s5, one with lower the expected Molydenum and one with higher than expected Vanadium. Cloudhammer suspects this is an issue with their steel distributor, and apologizes for not independently testing their materials before processing. This also means that while we initially thought this affected only 70cm katana blades, it might affect all s5 swords sold from July of 2023.
Samples from these batches were abusive tested before sending to us, so as long as previously purchased blades are not setting bends or chipping easily, they should be ok.
They are now acquiring more s5 and will metallurgically test samples before and after forging to ensure there's nothing in their manufacturing process that could be contaminating samples.
If you've bought s5 swords from Cloudhammer in the past and have had no issue with bending or chipping, we will offer you deep discounts on a future s5 purchase; if you have had these problems, we will replace them.
We humbly ask for patience in this matter, because this does take some time.
RVA Katana and Cloudhammer apologizes for any inconvenience
Update 4 (May 26, 2025): Cloudhammer has learned that there is another mill making steel whose composition falls within the specs of Hudson's s5, except for having low moybdenum (helps prevent corrosion and maintains performance at high temperatures). Based on metallurgical testing of blades late last week, they suspect their distributor sent them this steel.
Last year, as they were modifying heat treatment of s5 to increase hardness and edge retention, they did abusive testing, and are confident that these swords are extremely tough . You can see some of their testing in these two clips:
They have already made and heat treated several prototypes and abusive-tested.