i presume that you are using the traditional method of either CHATKA
(by acid, for plain gold jewellery) or GILLIT (by cynide, for studded
in my view you should opt for electroplating of gold.there are
acid,cynide as well as some nuetral processes available,wherein if
your pieces are having good surface finish (i.e.deburring,buffing
etc.)then you can get excellant colour and finish.also you will get
uniformity and durability.
there are many plating chemicals companies to choose from.i had
suggested a company to UMA MAHESHWARI (your Q.C. department) in an
earlier thread in this forum (page 7 november 2005), you can contact
them and get detailed info.