Also gold is super expensive! Currently about times more expensive than silver. When heated up, in the presence of oxygen in the air, a black oxide forms on the surface of copper, this is called firescale. This oxide can be a problem when enamelling, although it can also be the source of cool effects, so most often it is carefully removed before enamelling learn more about shaping and preparation of copper bases in this class.
When firing the first layer of enamel again firescale is produced, and you will see the surface becoming black, and then the oxide being dissolved into the enamel flux, which is formulated for this purpose. On the next layers, the surface of the metal, where covered by enamel fused to the surface, is not in contact with oxygen from the air anymore, so no further oxide is formed.
So what is an alloy? A mixture of metals molten together. This is done for many different reasons. When you mix two or more metals, their properties change, sometimes in surprising ways. Silver and gold alloys are much harder and thus durable than they are when pure. A couple of very common alloys are sterling silver and 18k gold.
Sterling silver is parts silver out of , and the rest, most often, is copper. Both of these alloys can be enamelled, but since both contain proportions of copper, they both get firescale when heated up. The firescale in these copper-bearing alloys is not as strong as on pure copper since the amount of copper is small, and often the enamel will absorb it with no problems, although the colours might not be as brilliant as on pure silver and gold, but for jewellery purposes sometimes concessions have to be made in the name of strength and durability.
This will depend on the design. One way to get around these tarnish problems is to perform an operation called depletion gilding, in which copper is removed from the very surface of the metal.
Another thing to have in mind is that these alloys are often the product of casting processes. In these we might have problems of porosity, depending on the technology used, and this can be a huge source of headaches.
Burnishing the surface might help, as is done also when enamelling precious metal clay, which is fine silver but also very porous.
Also of note, fine silver and fine gold are often used in the form of foil and wire for specific techniques. Yes you can enamel brass. Brass is an alloy of copper and zinc. Zinc is an enemy of enamel. However, when the concentration of zinc in the brass is small, we can enamel it. Traditionally, medals, both military and civilian, and badges of many kinds, for example for cars and this is still done for luxury cars were enamelled on what is called gilding metal or tombak, and then gold or silver plated.
Unlike pure copper, surprisingly, red enamel applied directly can work beautifully on gilding metal. Which brings us to…. When enamelling these metals, we will observe some unfortunate reactions due to the chemical interactions taking place with elements in the enamel.
I will be talking about the reactions that happen when we apply colours directly on the metal. To avoid these reactions, we apply a layer of flux as an isolation layer. Now have in mind that when talking about alloys, reactions to all the metals contained might take place, in function of their proportions. Testing is always necessary, and these are just things to keep in mind. And to test, we make colour palettes. You can watch my free video in which I explain how I make my colour palettes.
My palettes are very complete due to the nature of my work, but each enameler adapts these to best serve their purposes. Making palettes is a great beginner project. As a further note, none of the reactions I am going to talk about apply to opaque enamels. So you can use them without worries. When you apply red, pinks, yellows and some oranges directly on silver, you get a nasty reaction and the enamel might turn unevenly orange, slightly opaque, or nasty altogether, in a most often quite unattractive manner.
There are some exceptions in the red and pink range, very few and far between. So those can be applied directly on the silver. Opalescent enamels also turn yellow and nasty. Again there are a very few exceptions in this already very small category of enamels. For this reason, when working with these warm shades and opalescents, an isolation layer of flux especially formulated for silver is used. Unless a reaction takes place, silver is a white metal and transparent colours will generally appear as they are, unaltered and true.
Nothing reacts to gold! It is indeed a dream metal to enamel on. However, there is no going against the laws of physics. When you enamel on gold with transparent colors, the yellow of the gold will be visible through the glass. Blues will tend towards teal, bluish reds will turn more vermillion or orange, if you want a neutral green you will have to use a more turquoise enamel, etc. You can use a color wheel as a guideline.
The real problem is violet, which is the complementary of yellow and most often you will get an ugly color. Again, testing is necessary.
So as we said, copper generates firescale. A good copper flux will absorb it all through a sufficient layer and a good fire at high temperature.
However most transparent enamels will not be able to. There will be some staining, opacification, or other effects, which can indeed be interesting. A few colors can absorb all of the firescale, acting like a flux, and will look absolutely beautiful. Intense cobalt blues generally are able to. Other colors that can do this are few and far between find a nice selection here. For this reason, flux is often applied as an isolation layer on copper.
As a final note, new enamels are constantly being developed, and often surprising effects can be found in the new ranges of unleaded enamels, so keep an open mind for new developments in this field. Another aspect I am gonna briefly touch upon is the heat source, which we need to fuse the enamels to the base metals.
These temperatures typically range between and degree centigrade. The most controlled way to achieve these temperatures and hold them is an enamelling kiln. These are very insulated chambers with coil elements that heat up through electricity, and a door that can be opened to put the pieces in. In enameling, unlike in ceramics, we place the pieces in the already up to temperature kiln, and the firings are comparatively very short, not hours or days, but just seconds or minutes.
Thus it is important that the door of the kiln is on the side, and not on top. Fire sufficiently to dissolve all copper oxide reddish-brown color. One or two re firings may be required. It should be fired sufficiently to dissolve all copper oxide.
These cadmium selenium colors and will darken with prolonged firing. Edges commonly are black on copper and silver. If applied thin on copper they may appear black. If fired on silver they may appear brown. It is best to use these colors over a base coat such as for copper and for silver.
They should not be over-fired unless the darker coloring is an effect one is seeking. They chemically react with copper and silver and turn opaque. They will remain transparent on gilding metal, and properly prepared high karat gold and over a clear or opaque first coat for a limited number of firings. They will darken with prolonged exposures to heat. The opaque colors are: , , , , , , , , and These colors should be used on top of when working with silver. The transparent colors are: , , , , , , , , , , , , , , and When the transparents are used directly on copper they frequently appear opaque.
The color red is created by colloidal gold. The copper oxides which are taken into the solution of the glass collects on the colloidal gold. Several firings are required to dissolve those oxides back into the glass. There must be sufficient glass for this to occur. This is why a second coat may be required after the first firing.
If the color shows no signs of clearing after two firings, increase the time, not temperature. All of the gold bearing transparent colors are clear on gilding metal. When used over another enamel they tend to be more pastel and less intense as a color except for , and They should be used over opaque white, or over clear for silver.
Silver salts that are taken into solution of the glass during firing, impart yellow to gold bearing transparent reds, which makes the red look more orange red. To eliminate the yellow, use these colors over opaque white or clear for silver.
Some colors change color depending on how long and hot they are fired. This may be more of an issue when using a torch as you do not always know how hot you are firing. An example is Robins Egg. When fired on the cool side the color is more green. The hotter and longer you fire it becomes more of a blue.
When enamel cracks it is because there is too much stress in the glass and the glass has no choice but to relieve that stress by cracking. This can happen with any enamel under certain conditions. Under the conditions of heat the metal expands. The enamel flows and is carried with the metal. As the piece cools, the enamel becomes rigid between degrees F.
The metal continues to contract. This puts a strain on the enamel and given certain conditions, the enamel will crack. The reasons can include — wrong alloy or base metal; no counter enamel; the wrong expansions relationship; uneven or too thick enamel application; uneven enamel thicknesses back to front; non uniform base metal thickness; solder joints; weighting the enamel after firing; metal inclusions in the enamel; impact; the list can go on and on.
There is not a general answer that will cover all situations. To understand what is causing the cracking involves looking at each instance of cracking individually, and looking at all the conditions that may be causing the cracking or contributing to it. The greater the thickness of the enamel in relationship to lesser thickness of metal is worth considering. Slow cooling is best as well as lower temperature when possible which would obviously decrease the amount of expansion which decreases the amount of contraction.
When questions come in to Thompson regarding cracking or other presumed failures of the enamel or the process, and after the problem has been described, very often the caller adds that they are experienced enamelers and have been enameling for many years.
Their claim is always that this has never happened before, and that nothing has changed on their end. I do empathize with the caller. I have been where they are. You do all this work and suddenly something goes wrong and all is for naught. Frustration takes over and often puts a hazy cloud around the facts of what took place. Emotion can blind the person to objectively looking at everything that could have contributed or caused the problem.
Most customers want to blame the enamel first, but that is rarely the cause. There is almost always a reason for the problem that can eventually be found. When we ask a lot of questions we do not mean to trivialize the enameling experience of the customer, we are just trying to investigate anything that might be relevant to correcting the problem.
Customers with the worst problems are those that are working on the edge of what is doable such as using our enamels on brass or alloys of brass, trying to coat copper wire, applying enamel too heavily, etc. Another common problem is their work was not designed to be enameled. There was no consideration in the design of the piece as to how the enamel could be used successfully. When we ask questions, the answers need to be very specific and usually a good photograph can provide information that may not have been considered in the questions.
Collectively sometimes answers to the above questions can lead to an answer as to what caused a problem. The Liquid Metals — Bright Liquid Gold and Bright Liquid Palladium are liquids applied with a brush or crow quill pen onto a glass surface, when fired produce a thin metallic coating fused onto the glass surface.
The Mother of Pearl M creates a rainbow iridescence of colors. The colors are subtle and are seen best when the piece is held at an angle in light. They show up best on an opaque white enamel such as opaque white. These products are applied to a glass surface with brush or pen onto a glass surface.
There is an organic binder in these products that must be burned out slowly, to prevent an irregular or flawed coating. Dry the piece in a dryer or on top of the furnace. This is done by moving the piece into the mouth of the furnace for only 3 or 4 seconds. This is repeated several times to slowly heat the piece up to the temperature that the organic materials will burn out.
The piece is then fired for 1 to 1 minute, 15 seconds long enough for the underlying enamel to soften. If using on fused glass, the kiln should be vented until the temperature has reached degrees F. The temperature is then taken to to degrees F. Good ventilation is suggested for firing onto enamels on metal and glass fusing.
The Essence for thinning M is used to thin any of the liquid metals as they become thick with use and exposure to air. Use a drop or two at a time and stir with toothpick. Brushes used with the liquid metals may be cleaned with turpentine, paint thinner or lighter fluid. Carefree Lusters are titanium coated mica flakes. They are not glass and as such do not stick to each other during firing.
Residue is expected after firing which is washed off. They are applied as the last application on top of a glass surface. They loose their luster if enamel is fired on top of the lusters. The may be applied onto an enamel on metal surface, glass surface or ceramic glaze.
They also come in solid and patterned decal sheets. The watercolor lusters are used by adding a drop or two of water into the tub of luster-wax cake. Allow a few minutes then apply to top coat of work with a brush. Dry -fire at degrees F. After cooling, take piece to sink and rinse off residue luster.
The dry powder is the same material as the water colors or decals. Powders should be mixed with a painting medium — oil or water base of your choice. Same application and firing procedures — same results as stated above. The Glass Painting — Enamel Powders GPP series are finely ground glass finer than flour powders than are meant to be mixed with a medium for application:. These enamels are low fusing and low expansion.
GPP powders are opaque colors but light will pass through them on glass. Colors are most vibrant on an opaque white glass. They are not as vibrant on clear glass. For dry powder painting enamels and pigments some form of wet medium is necessary to make painting possible.
Many materials could be used. The primary requirement for enamel painting is that the medium will not leave any ash after firing or will not create bubbles in the glass after firing. Painting mediums can be either water or oil based. Water mediums are good for washes, and have no odor when using.
Oil based mediums allow more working time and they disperse the powder in a more controlled manner. Sharper, thin lines can be achieved. The squeegee oil is more viscous than most of the other oils. It is the oil used in the E series — oil base. It is the best oil to mix powders with for use in a crow quill pen.
The screening oil is a refined squeegee oil which allows for better resolution and less spreading or blurring of the oil after painting. Lavender Oil A is good for fine details and smells like lavender. Clove Oil A is good for washes and smells like cloves. Painting Oil for Miniatures A is good for miniature style painting where extremely minimal oil is to be used. Hi Patsy, I have a vintage trinket box made in India that I would like to restore the paint on.
Can it be done? Is it worth it? I can send you pics when you have the time. Thank you for your time. Bonnie I would not be able to repair the box. Most of the time it is more expensive to repair than to cost of the box.
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