451°F. That’s all it takes to wipe out your bitcoin forever.
Paper ignites at 451°F. House fires burn at 1,100°F. That seed phrase in your drawer? It’s not a backup, it’s a countdown.
For about $30 and two hours of your time, you can stamp your bitcoin seed phrase into stainless steel and stop worrying about it forever. This guide shows you exactly how, using the Blockmit Washer Jig — the most popular DIY metal seed backup in the bitcoin community, and the one blockmit.com officially recommends.
Paper Backups Will Get You Rekt
Most hardware wallet users write their seed phrase on the card that ships in the box. That paper card goes in a drawer, a safe, or under a mattress. And then life happens:
- House fire — paper ignites at 451°F. Your seed is gone before the fire trucks arrive.
- Flood or water damage — ink bleeds. Paper disintegrates.
- Fading over time — ballpoint pen on cheap paper doesn’t last decades. Your bitcoin has to.
- Accidental destruction — someone throws it out. It gets wet in a move. It disappears.
This isn’t fear-mongering. This is self-custody math. You took the step to hold your own keys — the paper card is the weak link that undoes all of it.
304 grade stainless steel doesn’t burn. It doesn’t rust, corrode, or fade. It survives house fires, floods, and decades in storage. This is what how to stamp your bitcoin seed phrase into metal — and what self-custody actually looks like in practice.
What You Need (Full Shopping List)
1. Blockmit Washer Jig — $4.99
Get it at CryptoCloaks
Two jigs included — one to use, one backup if you miss a stamp. Holds M8/24mm washers in perfect alignment so every letter lands clean and readable. 4.88 stars across 25 verified reviews. This is the jig blockmit.com recommends on their official guide — the original project points here by name. Ships from Colorado. Available in 17 colors. $4.99.
2. 1/8″ (3mm) Letter Punch Kit — ~$20
Available on Amazon. You specifically want 1/8 inch (3mm). These are sized to fit 8 letters across a standard washer — exactly enough, because BIP39 words max out at 8 characters.
3. M8/24mm Stainless Steel Washers — ~$5-10
Your local hardware store. 304 stainless steel. You need 24 washers for a 24-word seed (12 for a 12-word seed). Grab a few extras for practice and mistakes.
4. Stainless Steel Bolt and Nut
An M8 bolt with a wingnut to stack and secure your washers in order after stamping.
5. Anvil or Steel Block
A small anvil, railroad track chunk, or heavy steel block. You need steel on steel — wood absorbs impact and produces weak, unreadable stamps.
Total: approximately $30-35 (not including anvil, which you may already have)
Step-by-Step: Stamp Your Seed Phrase
Step 1 — Set Up Your Workspace
Solid, stable surface. Steel block on it. Zero wobble. Get your BIP39 word list out (from your hardware wallet setup) and plan your washers. Each washer gets one word. Mark washer #1 before you start — order matters more than anything else in this process.
Step 2 — Load Your First Washer
Place a washer into the Blockmit jig. The jig’s channel holds it perfectly flat and square, with evenly-spaced letter slots. This alignment is why your stamps come out clean — without the jig, letters wander and overlap.
Step 3 — Set Your First Letter
Load the corresponding letter punch into the first slot. Hold it perfectly vertical — 90 degrees to the washer surface. Any angle and the letter skews.
Step 4 — Strike Once, Hard
One firm hammer strike. You want a clear, deep impression, not a timid tap that leaves a ghost mark. Practice on a scrap washer first. Get the feel of how much force you need. Move to the next slot. Repeat for every letter in the word.
Step 5 — Work Through All 24 Words
Remove each completed washer, set it face-up in order, and repeat. Keep them in sequence as you go.
Step 6 — Assemble the Stack
Thread all 24 washers onto your bolt in order (word 1 on top). Add blank washers as covers on each end to protect the stamped faces. Secure with your nut. Your seed backup is now a single, organized, indestructible object.
The First 4 Letters Trick
Many Bitcoiners only stamp the first 4 letters of each BIP39 word. Every word in the BIP39 list is uniquely identifiable by its first 4 characters — you lose zero information. You cut your stamping time roughly in half. This is standard practice in the community.
How Does It Stack Up? (Jameson Lopp’s Tests)
The Blockmit washer method uses 304 stainless steel — the same material class that earns A grades in Jameson Lopp’s independent metal backup stress tests (heat, corrosion, crush resistance). Here’s what you’re comparing against:
| Option | Cost | Grade (Lopp’s Tests) |
|---|---|---|
| Blockmit DIY (jig + stamps + washers) | ~$30-35 | Equivalent to A-grade |
| Blockplate | $79 | A |
| Coinplate Alpha | $79 | A |
| CryptoTag Zeus | $130 | A |
| CryptoTag Thor | $350 | A |
You’re not buying a lesser product. You’re doing more of the work yourself. The protection quality is equivalent. The cost difference is real.
If you’d rather skip the DIY and go purpose-built, the CryptoCloaks 1″ Washer Stamping Jig is a premium option — and the Seedor Safe is our polished, no-DIY-required seed storage solution.
Mistakes That Will Ruin Your Backup
Wrong stamp size. Get 1/8″ (3mm). Larger stamps won’t fit 8 characters across a standard washer. If you’re unsure, the product page links directly to the recommended kit.
Stamping on wood. Always steel on steel. Wood absorbs impact. Weak impressions become unreadable impressions.
Losing washer order. While loose, one mix-up makes your entire seed wrong. Keep them numbered and in sequence until they’re on the bolt.
Storing both copies together. If they’re in the same location, you don’t have a backup. You have two originals in the same risk zone.
Why CryptoCloaks?
- Bitcoin-native: We accept bitcoin. We think in sats.
- Made in Colorado: Real location, real people, real accountability.
- 4.88 stars / 25 verified reviews on the Blockmit Jig alone
- Official recommendation: blockmit.com points here by name
- Ships next business day from our Colorado shop
This isn’t an Amazon dropship product. It’s a community tool, made by Bitcoiners, for Bitcoiners.
Get Your Jig
Get the Blockmit Washer Jig — $4.99 at CryptoCloaks
Two jigs. 17 colors. Ships from Colorado. The most affordable entry point into real metal seed storage — and the one the original project recommends.
Not your keys, not your coins. Your keys deserve better than a paper card in a drawer.
Pricing as of March 2026. Stamp kit pricing may vary. Always verify seed phrase backup procedures with your specific hardware wallet manufacturer.