Involvement:Expert (understands the inner workings) - Ownership:1 day to 1 week
- Can be used to make practical jokes. - Very cheap.
- Low quality of the 'pen'.
- Some of the ink has leaked in transport.
This disappearing ink is probably based on thymolphthalein - commonly used pH indicator. It turns blue above 10.5 pH, and turns colorless below 9.3 pH. When you drop it somewhere, then carbon dioxide from the air react with it and lower pH.
If you need it then buy it! You may want to buy spare ink bottles (SKU.8587) as well. But better make a separate order for it, because the bottles can leak and damage rest of your items.
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