pitubo wrote:Jees wrote:I wonder if the hot mimo soup is factor to the color by dumping the NaOH in all at once, in that stage the FB deems got warmer than the regular pull temp. Going gentler next time?
For best results, dissolve the lye in a steel container and mix it into the mimosa soup after the lye has completely dissolved and the lye solution has cooled down sufficiently.
While steel or iron are very resistant to lye solution, care should be taken when selecting a metal vessel for handling them.
It should be noted that stainless steel is merely
resistant to corrosion, as it does not form a protective black oxide layer. Strong lye solutions can cause corrosion stress fractures in thin stainless steel containers of most types under heat (such as that caused by adding lye to water). Stainless steel flasks and drinking containers should not be used for handling strong bases during reaction, as this can cause a sudden and rapid rupture in the metal, especially near seams or welds.
Galvanized steel is common for making buckets and tools, and contains zinc. The zinc will react with the lye and leave a bunch of Sodium Zincate in your solution.
Solder and other metals used in steel tools can be
highly vulnerable to corrosion, however (this is why pure lye is not recommended for cleaning copper/tin plumbing). Aluminum, brass, bronze, tin, zinc and cadmium are commonly used in metal fittings, fasteners, welding materials and solders, and are all vulnerable to corrosion by lye.
These reactions produce chemical contaminants and gaseous by-products which can cause a potential fire hazard without ventilation, and can quickly turn a great extraction into a toxic mess (Take my word for it, I've been there before).
Aluminum containers should never be used to handle strong bases. It's just all bad; Trust me.
Here is a MSDS for Sodium Hydroxide solution
(link), and a reference for the chemical resistance of stainless steel, as well
(link).
Furthermore, in the presence of heat and oxygen, alkali metals can cause a dark oxide layer to form on steel that can be very hard to remove (this is called bluing). While it's not likely to contaminate your end product, it's worthy of noting when selecting a container. There are commercially-available products to remedy this problem, which are most commonly available at firearms and gunsmithing stores.
....When in doubt, use pyrex.