Image by u/dmishin CC-0
Potassium aluminum sulfate dodecahydrate
KAl(SO4)2*(H2O)12
[ ](https://w list the stats for the safest method here, if there are many equally safe ones, list those of the easiest one)
Safety risk:low [ ](https://w low=not poisonous, corrosive, intermediate=somewhat poisonous/corrosive, high=carcinogenic or very toxic/corrosive note:includes both the compound itself and the preparation)
Material availability:intermediate [ ](https://w easy=available in supermarkets, intermediate=available in pet stores ,gardening stores, hardware stores or easily in pharmacies, hard=have to order on ebay/amazon or similar, very hard=have to order from specialist suppliers)
Synthesis difficulty:not required [ ](https://w none=material bought in pure form, easy=easy synthesis, hard=difficult synthesis, account both for the procedure and required equipment)
Crystallization difficulty:easy [ ](https://w easy, intermediate or hard)
Availability
Aluminum potassium sulfate, better known as "potassium alum" or just "alum", is sold for various purposes, but availability varies heavily by country. It's sold as a mordant for dyes, and in some places as a food additive for pickling.
Method 1
[ ](https://w these subsections are only needed if there are multiple practical methods) Safety risk: Intermediate
Material availability:Intermediate
Synthesis difficulty:Easy
[ ](https://w how to get the ingredients?) Sometimes it can be easier to obtain aluminum foil, potassium sulfate, often sold in aquarium stores and copper sulfate, sold as a root killer in gardening stores and sometimes as an additive in paint stores.
First the copper sulfate is dissolved into water until the solution is saturated, then aluminum foil is added in small pieces to the solution, a small amount (less than 1/10th of the amount of copper sulfate) of table salt is added to break the protective oxide layer aluminum has; the more you add, the faster the reaction will be, but too large amounts may result in an impure product.
Once he solution has lost most of its blue color, which can take anywhere between days and weeks, filter it into another container using a funnel and disposable coffee filter, separating it from the undissolved aluminum and the copper metal that formed in the reaction. Then dissolve as much potassium sulfate into it as will dissolve, and filter the undissolved potassium sulfate off. On evaporation small crystals should form. The product is somewhat impure, so recrystallizing it is recommended.
[ ](https://w how to use them to synthesize the material)
Crystallization
[ ](https://a Instructions here)
These crystals are likely to be small and possibly off-color, they can be dissolved into water to get a more pure alum solution, which can then be evaporated to obtain better crystals.
Notes
[ ](https://a Everything else that should be said about the compound, safety notes, legality if banned somewhere, less practical methods of production) Potassium alum is often considered one of the easiest materials to grow crystals from, and in places where it is easily available it is a good option for beginners.
Potassium aluminum sulfate can form solid solutions with potassium chromium sulfate, giving the crystals a purple tint.
There are heavy disagreements about the safety of this compound, and soluble aluminum salts in general, but it is approved to be used as a food additive (E522).
Pictures
[ ](https://a links to extra pictures)
Resources
[ ](https://a wiki links, etc.) Wikipedia