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Adam Savage’s Tested
Adam Savage Builds a Demon Core!
⏱ 74 min video · 3 min read20 May 2026Worth watching
TL;DR
Adam Savage machines a museum-quality replica of the Los Alamos 'Demon Core' transport case — a magnesium box originally built by machinist Ralph Sparks to safely carry the plutonium core intended for a third atomic bomb. The build spans multiple days of milling, threading, and finishing work on Rich Light phenolic material, culminating in a crackle-painted box with working urchin initiator ports and a tungsten alloy sphere standing in for the actual plutonium core.
Key points
1
Savage received a 3.5-inch diameter tungsten alloy sphere (90% tungsten, 7% nickel, 3% iron) from Midwest Tungsten Service that precisely replicates the weight of the actual demon core — approximately 14 lbs.
2
The original transport cases were built by Los Alamos machinist Ralph Sparks out of magnesium (transparent to gamma rays) with cooling fins; at least three boxes were made — one black crackle finish for the gadget core, two bright yellow.
3
Savage machined the box from Rich Light phenolic, cut a precise hemispherical seat using a radius cutter calibrated with gauge blocks, and fabricated four functional threaded urchin initiator ports in aluminum inserts flush with the top surface.
4
The crackle finish formula used is PJ1 Fast Black — two coats 3 minutes apart, then baked at 125-150 degrees for about an hour.
5
Savage credits three other makers whose research shaped his build: Fuzzy Raptor (3D printed version on Printables), Adam Parseek (machined version with water-cut stainless handle), and Ross Sacket (RPF, 2017 yellow version).
Actionable insights
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When cutting internal threads in aluminum, slow down near the finish — excess friction causes galling that ruins the threads.
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To machine rubber stoppers, freezing with liquid nitrogen is unnecessary — a standard drill bit works cleanly on rubber corks at room temperature.
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For a crackle paint finish replicating period military equipment, use PJ1 Fast Black: two coats 3 minutes apart, bake at 125-150 degrees for one hour.
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Setup is everything in precision machining — Savage lost significant time by discovering a fundamental measurement error only after resetting and rechecking all gauge block stacks.
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Deep prop research requires iterative search term refinement over weeks; key breakthroughs often come only after enough contextual knowledge accumulates to recognize what a photograph actually shows.
Notable quotes
“It will sink into you just how much human brilliance and ingenuity and collaboration and cooperation and breaching of the vanguards of knowledge all to the end of harming other people. And it's so sad and it's such a tragedy.”
“I sent a picture of this to Kyle Hill and he was like, 'Dude, that's museum quality.'”
“I have to look at something for months and search Google for it endless numbers of times until my eyes are new enough to figure out what information I haven't yet discovered.”
Worth watching?
✅
Worth watching the full video?
Watch if you enjoy watching expert-level machining combined with genuine historical research — the fabrication problem-solving is satisfying and the Manhattan Project storytelling adds real depth beyond a typical build video.
Saved you some time? The creator still deserves a like.
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