Lye a common name for a solution of Sodium Hydroxide dissolved in water.
If you are making lye from NaOH solid granules or pellets its not as simple as just measure out the quantity and dropping it all in the water.
As NaOH dissolves it produces heat so you will need to be able to cool your solution so it does not boil.
This is a good example of an exothermic reaction, a reaction which releases energy as heat.
NaOH must be added slowly to the solution waiting to allow the solution to cool and the pellets to dissolve.
Alkali + metal = Hydrogen gas + metal oxide
You should not use a metal container because metals such as aluminum and zinc (galvanized metals) will corrode rapidly and produce Hydrogen gas.
Stainless steel will not corrode quickly but will produce hydrogen gas which is an explosion hazard.
The creation of Lye also produces some aerosols which will contain corrosive Lye.
Do this is a well ventilated area.
Maximum solubility of NaOH at room temperature (20C) is 111g per 100mL of water.
Where can I get NaOH to make lye?
Quite easily surprisingly.
Most super markets have it in the cleaning products section look for the drain cleaners.
Even smaller convenience stores will often carry this product.