This video documents an attempt to create a functional knife blade from lapis lazuli as part of a series testing different materials for knife-making. The creator acquires a large, high-quality piece of lapis lazuli and uses a five-axis water jet to cut out the blade (a tonto shape) and handle scales. Challenges arise due to the material's hardness and brittleness, leading to difficulties in sanding and the primary blade breaking during shaping, requiring repair with glue. A secondary knife is also created by crushing lapis lazuli scraps and mixing the powder with resin, forming a more durable composite blade. The pure lapis knife is reinforced with carbon fiber and resin for the handle, while the resin/lapis blade is given a polycarbonate tang. Both knives are then sharpened using diamond plates and tested on various items (tomato, cucumber, chayote squash). The pure lapis lazuli knife proves surprisingly sharp, capable of making very thin cuts, while the resin/lapis composite knife is thicker, less effective, and its resin component softens when exposed to heat. The video concludes that pure lapis lazuli can indeed be sharpened into a highly effective, albeit fragile, cutting edge.
Crafting Knives from Lapis Lazuli: Process, Challenges, and Surprising Results
0:00 Project Goal: The creator aims to turn lapis lazuli, a hard but brittle mineral, into a sharp knife as part of a series testing various materials for knife-making.
0:33 Acquiring Material: A large, suitable piece of lapis lazuli is sourced from eBay.
1:11 Material Inspection: The lapis lazuli stone is shown, noting the presence of pyrite (fool's gold) and its solid blue color, which is expected to maintain intensity even when sharpened thinly.
1:58 Water Jet Cutting: A five-axis water jet is used to precisely cut the tonto-shaped blade and handle scales from the stone.
3:26 Initial Shaping & Challenges: Attempting to sand the stone by hand is slow; a belt grinder is used, but the material is difficult to work with and prone to cracking/breaking.
5:04 Backup Knife Plan: Due to the fragility, a second knife is planned using crushed lapis lazuli scraps mixed with resin to create a more durable composite material.
5:38 Lapis Lazuli Pigment: A fun fact is shared about lapis lazuli historically being a primary source for blue pigment, used by artists like Vincent Van Gogh.
6:14 Crushing Scraps: Lapis lazuli scraps are crushed using a mortar and pestle to create a powder for the resin mixture.
6:57 Resin Pouring: A mold is made, and the lapis lazuli powder is mixed with resin and poured to create the composite blade blank and fill parts of the main knife's handle.
8:39 Resin Curing: The resin cures, resulting in a composite material that resembles liquid lapis lazuli with embedded particles.
9:08 Assembling Knives: The main lapis blade gets handle scales potentially using the resin composite and carbon fiber; the resin/lapis blade is planned with a polycarbonate tang.
9:40 Continue Shaping: Excess material is removed from the handles and blades using the belt grinder. The pure lapis blade gets a bevel and initial sharpening.
10:14 Primary Knife Breaks: The pure lapis knife blade breaks during grinding, requiring gluing it back together (not shown).
10:44 Resin Knife Challenges: Sanding the resin/lapis composite knife is difficult as the resin softens when heated by the grinder, causing the blade to bend.
11:38 Polishing Polycarbonate: The polycarbonate tang is sanded to become clear.
11:51 Handle Detailing: Divots are added to the carbon fiber handle scales using a Dremel for texture and grip.
12:38 Sharpening: Both blades are sharpened using diamond plates of increasing grit (300, 600, 1200).
13:09 Final Look: The finished knives are shown, highlighting the clear polycarbonate tang on the resin knife.
13:33 Testing Materials: Tomato (soft), English cucumber (medium), and Chayote squash (hard) are chosen for testing.
14:07 Tomato Test (Pure Lapis): The pure lapis knife cuts the tomato "like a dream," making very clean, paper-thin slices, demonstrating surprising sharpness.
14:58 Tomato Test (Resin/Lapis): The resin/lapis knife is thicker and less effective at cutting thin slices, but still manages to cut the tomato.
15:39 Cucumber Test (Pure Lapis): The pure lapis knife glides through the cucumber easily, making extremely thin slices.
15:57 Cucumber Test (Resin/Lapis): The resin knife is noted as a "chunker" and requires holding at a weird angle due to its thickness, performing worse than the pure lapis knife.
16:37 Squash Test: The hard chayote squash is attempted. The pure lapis knife cuts through it surprisingly well, even through the seed.
17:23 Squash Test (Resin/Lapis): The resin knife struggles with the squash, as the resin softens in the sunlight, making the blade too flexible.
17:36 Conclusion: The creator is highly satisfied with the pure lapis lazuli knife, rating it 10/10 for its sharpness, despite its fragility and the challenges in making it.