I am sure that you have all at one time or another had problems with firescale and/or related issues on your jewelry, and no matter what you try, as much as you clean the items, the problem remains, or it might temporarily go away but within days ugly staining returns on your product. Frustrating I know, and the real problem is whatever you do at this point it is to late… it’s a bit like closing the barn door after the horse has bolted…. There are no real fixes at this stage, the issue is in metal handling control by your manufacturer who needs to ensure the problem does not occur in the first place.
I am going to explain a little here about steps manufactures can take to prevent these issues, and a few tools, or good questions you can ask them to see if they are doing things correctly. Many manufacturers might say that to follow correct procedures as broadly outlined here will increase prices, and that might be true, to a point, but from experience I can tell you that any extra manufacturing costs are more than offset by:
- From the manufacturer point of view: the reduction of rejections during production and the decrease of the heavy cost of remaking
- From the customer point of view: a much better result which will lead to fewer returns and less time spent with a polishing cloth in hand, and less end customers complain.
The actual savings are huge, the peace of mind you get that comes from knowing your product is reliable is absolute gold.
It all starts out with where and how your manufacturer buys their metal. I am going to refer to silver as being the metal in this letter as it is probably the metal that incurs the most issues with incorrect handling and contamination, and is the one where bad handling is most visible in the final product, but in actuality all metals face the same issues. When buying your silver, always make sure you can trace it back to the refiner and ensure that it is a refiner of good repute. There are two main reasons for this, one is metal contamination, or impurities, and the other is oxygen content. Oxygen is sneaky, and a very reactive atom that manages in its ubiquitous way to be everywhere, and that is a good thing for us as without it we would not be living on this wonderful planet, but it is not good for your jewelry quality, as it reacts with all metals to form oxides which cause discoloration, copper oxides, silver oxides etc. and also iron oxide, which we are all very familiar with as rust. Neil Young could have rephrased it from Rust never Sleeps to Oxides never Sleep, and this is why cutting rust out of a panel in your car and repainting it or trying to polish firescale off your silver jewelry can be a very fruitless and frustrating endeavor, oxides once they are there don’t sleep and will keep coming back! So we need to ensure from the very beginning we have no oxygen in our metals, and then follow procedures during manufacturing to restrict metals from oxygen exposure. An industry benchmark for purchasing raw silver (actually most metals) is 300ppm (parts per million) oxygen content and at this level you are starting in a good place. The 2nd point here is contamination, your fresh silver should be 4 nine’s or 99.99% silver, this is also an industry standard as the remaining 0.01% is too small to give any serious production issues.
Non Destructive Metal Assay
As an aside here we run a metals assay service at Kapit Mas where other manufacturers can come in and test the purity of their products, and it is incredible how many times we get a result of less than 925, on finished product, but the manufacturer swears and declares they did the mix correctly… So we invite them to bring in some of the raw silver they buy for testing and often it will come out at around 98% and that remaining 2% can include contaminants like nickel cadmium and iron. Cadmium, highly toxic, is illegal in many countries but often used as a solder, and not easy to remove when refining. Iron is also not easy to remove when refining and is often coming from scrap when workers are using files with a steel content, and as we now know from above, having iron contaminants is like putting rust in your product..!
The next step to think about here is alloys: what are we mixing our silver with to bring it down to 925? Are we choosing a high quality de-ox alloy, or using some creative recycling and using old copper electrical wiring from a demolition site? Again it is very important to ensure your material quality Copper sucks up oxygen like a sponge sucks up water, you need to be very careful! Good quality –ox alloys from a reputable supplier will have ingredients that can help to keep oxygen content low. For the last 15 years we have used alloys from ABI Metals (ABI Manufacturing) abimetals.com and work closely with them to ensure a good result.
4 Nines (99.99) Silver with de-ox Alloy Grains
So in order to get a good result we need to start with good ingredients, pretty clear I think – just like baking a cake, the next step is to handle those ingredients with care, and again just like baking a cake, when you mix ingredients, it happens best when heat is applied, but also when heat is applied atoms get more excited and more mobile, and therefore more reactive, and just as baking ingredients can spoil, metals when they are hot – red hot, become liquid, more mobile, and yes more reactive, and the first choice of metal atoms to react with are oxygen atoms…. So… and here we get to the nitty gritty of good manufacturing processes and metals control. We need to severely restrict the exposure of red hot or liquid metals to oxygen, and if exposed does occur, and which for some processes may be impossible to prevent, the exposed metal should always head to scrap for refining and not be reabsorbed into the manufacturers base stock for reusing.
Good ways to prevent oxygen contamination include, when casting or graining, to use closed systems. A closed system is one where you melt your metal in a closed container/crucible, the method is to place your metal into the sealed crucible, vacuum out all the residual air and then pump in either nitrogen or argon, inert stable gasses that will not react with your metals.
Closed System Casting
If you are using open systems, then you need to always have a flame covering the top of the crucible holding the metal, the purpose of this flame is not to heat the metal, but to ensure you burn off any oxygen in the environment before it comes in contact with the hot metal. These steps will ensure your metals stay oxygen free until this point. But you will still have a few areas of risk such as buttons on a casting tree: after casting the tree is still red hot when it is removed, and the only part open to the air is the bottom of the button and this is where contamination will occur. You cannot control it, and therefore the material from such areas should go directly into your scrap bin and not be returned to your base stock. If you add fresh metal to this contaminated metal you then damage your entire metal stocks and your general metal quality standard will be reduced.
Open System Melting with Top Flame
The next part to control is at the bench work level, it is less important here from a metals stock point of view as the quantities of metal are less, but it is very important from the point of view of the individual jewelry item as any problem here will go directly to the customer/end user. The way to look after this area is simply to use as little heat as is required to get the soldering job done, and for the smith to limit the time and the surface area of metal to be heated. If it is a small join using laser or cold fusion welding is best, next step up for things like soldering jump rings or posts hydrogen welding is good, it gives a very hot but very localised flame which reduces the surface area heated. You will always need to do soldering work and for some intricate work with a lot of filigree, such as some of the traditional Balinese styles you will never get away from lots of soldering, and often for these types of design, firescale from oxygen contamination is hidden by the use of oxidization techniques to actually oxidize the silver, turn it back and give contrasting colour to emphasize the design. This can work well, but be aware to keep these oxidizing chemicals and the gases they emit during this process well away from other metals to prevent potential cross contaminations. A separate well ventilated room for this kind of process is recommended.
The big thing here is to keep soldering work to an absolute minimum, and when it is required to heat metal, do it for as short a time as possible and to as smaller surface area as possible. Lastly, to maintain the purity and quality of your production remove from your metal supply any material that has been excessively heated during bench work as it will be saturated with oxygen and just as rust never sleeps, if you put this back into your main supply with your fresh metal.. you will damage your precious new metal stocks.
While reading some of the above you might get the impression that I am against recycling of materials, but this is very far from the truth. Recycling, social and environmental awareness are very close to my heart, and are considerations in every decision I make, but if you are after quality, which is also something I strive for in every aspect, you must do your homework and know how your recycling is done and that it is done well. There is a lot of backyard metal recycling going on in Bali, and I am sure in other places too, which may sound great when you first hear it, but you really need to check how it is being done, where it is being done, and the environmental controls, how they are disposing of the noxious chemicals required to do this job, and what is the quality – oxygen content and metal purity of the final result. Is it good enough to allow you to make great jewelry? We work closely with some great suppliers providing recycled materials that meet all standards for production and for environmental controls, it can be a little more expensive, but the quality benefits, and the peace of mind far outweighs any extra cost. I like to say we are first and foremost Jewelers who are consciously green, rather than a consciously green organization trying to make jewelry, and this approach I believe although subtle in its definition difference, really establishes an approach which ultimately provides a better product and a greater benefit – for all concerned.
As always I hope this letter helps you out, and gives you some food for thought, and if you do have any questions, please don’t hesitate to get in touch.
Many good wishes,