Except for the Silver Nitrate, Bromide and Iodide, the formula has some leeway for error in Gelatin, water and in the exactness of the timing. But, whatever error you make, make sure you repeat it next time or you will not get the same emulsion.
Wash in cold Distilled Water. Tap water has Iron salts and chlorine.
Use 250 BI Oxidized photo grade gelatin for making the emulsion.