I want to make a tin ring like it´s golden. In CuSO4 solution it just turn black.CHRIS25 - 18-1-2015 at 10:29
Is this pure tin? Or is it pewter? If it is very old pewter it will have lead and I believe this might be the cause of the black. If it is recently
bought pewter (the last 10 years I think) It will not contain any lead, it will have about 92 - 96% tin, the rest made up of copper and antimony. Or
copper and bismuth. If it is the latter you could use liver of sulphur. Don't buy it, it is easy to make (if you want directions I will post them).
But it is sulphur + potassium hydroxide to make potassium polysulphide. making your own gives you much more freedom. This patina dip can take you to
the gold colour though with some trial and error.
tin
morsagh - 18-1-2015 at 10:58
It s tin from laboratory so i think it´s pure...CHRIS25 - 18-1-2015 at 11:54
Then I was wrong I suppose it must be the sulphide in the the copper sulphate that tuns it black. That's all I can think of. Where did you get the
idea that you give a gold coloured finish on tin with copper sulphate? morsagh - 18-1-2015 at 12:29
When you heat copper with zinc surface you will get gold color so... CHRIS25 - 18-1-2015 at 13:05
I really don't follow you here, ..."heat copper with zinc surface..." what do you mean? I thought this was about tin? When you heat copper you get a
specific order of colours develop (the reverse side is slightly different), the colours follow this order: Orange -red-blue/purple - dark red - deep
purple irridescent type look - sort of chestnut dark brown - red oxides and finally black oxides. There are quite a number of subtle phased colours
in between each of these, but this is a general overview. How did we get from copper sulphate with tin in it to a zinc surface all of a sudden? If
you are talking of solutions to patinate then I suggest potassium polysulphide as mentioned earlier for speed and durability. I just do not see how
copper sulphate will get you your yellowish gold look. Where did you read this? If you read this somewhere then I would suggest mixing heat and
solution. You could spray the tin with copper sulphate and heat the tin afterwards, you could heat the tin and then spray the copper sulphate, you
could place the tin in a hot solution of very dilute sulphate, there are many variables involved in patination but unless you point me to where you
got the idea I can not help, I googles this and could find nothing. I have never worked with tin, only copper so my reasoning is based only on my
years of patinating copper.
[Edited on 18-1-2015 by CHRIS25]cyanureeves - 18-1-2015 at 14:00
i'm all ears too and would like to know this process because i have a gold colored cup that has what appears to be silver plating substrate.the gold
finish is NOT gold as i was trying to strip it and didnt come of.morsagh - 18-1-2015 at 19:05
This won't work. Zinc wants to give up electrons easily and copper wants to receive them gladly. The zinc is reduced and the copper is oxidized. It
will never happen the other way around. If you google Reactivity series table you will visualize how this works. For example a common method to
extract silver metal from a silver nitrate solution is to place a clean piece of copper in it. The copper is oxidized and provides electrons into the
solution and displaces the silver out of solution which is being reduced. Silver will never displace copper out of solution. So if you grab hold of
this http://chemistry.tutorcircle.com/inorganic-chemistry/reactiv... it will explain a few things.
I only have one last suggestion for you that will produce a yellow, but it needs experimenting with, plave the tine on a hotplate or supply any source
of heat. Now, tin melts Very easily, (280 c or around there somewhere), the trick is to heat it gently, keep removing it and wait a few seconds then
heat again. Trial and error, but I remember from working with pewter ages ago that yellow oxidation appeared on scraps of pewter that were left over
from melting.
[Edited on 19-1-2015 by CHRIS25]MrHomeScientist - 21-1-2015 at 10:27
The gold color appears because the zinc alloys with the copper to form brass, which is golden in color. Tin and copper would make bronze, which may be
too dark of a gold for what you want.
With your experiment, the tin is able to displace copper from solution but this will be pretty slow. I just did this experiment myself not too long
ago - the tin did indeed turn black. I think this is from an extremely rough surface of copper metal deposited on the tin, which absorbs light. The
trick here may be to first find a way to get a good, smooth plate of copper on your tin, then heat this very gently (tin has a low melting point) to
hopefully form a layer of bronze. That's similar to how the video works; not really in "reverse". I don't know enough about plating to give you advice
on that part.
