You can fine sodium hydroxide online. You can purchase it at Amazon as sodium hydroxide or lye. Pure lye drain opener, caustic soda, and pure or food grade sodium hydroxide. Depending on your project, you may be able to substitute potassium hydroxide (KOH), which has similar chemical properties and is easier to find. However, these two chemicals aren't the same, so if make the substitution, expect slightly different results.
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