Tuesday, May 5, 2015

Let's Talk About How to Get Clear, Bright Enamels!

Today let's talk about the flame you get with a Hot Head torch.  This "single gas" torch has been around for about 40 years and is the workhorse of portable torches. Hooked up to a 1 lb. tank of MAP gas (propylene),   it is meant to be fired in an upright position.

Take a look at this video and then continue reading.  I hope the information is helpful to many of you who are making torch-fired enamel, but may be questioning … or reaffirming … your color results. :-)

There are three types of flames: an oxidizing flame, a neutral  flame, and a reducing flame.  When you light your torch, 99.9% of the time the flame will be at too great an intensity for general firing.  The flame is very loud … it's nearly roaring.  This is a reducing flame.  This bushy flame has an orange interior with yellow mini flames flashing at the edges. This fuel-rich flame has a lot of non-combusted fuel.  This extra fuel will be deposited in your beautiful enamel and turn your colors a muddy gray or brown.     

To reduce the flame intensity, turn the knob to the right. Turn, turn, that's right, keep turning.  Turn the flame down until it is nearly off; then turn the knob to left about a half a turn.  This is an oxidizing flame.  An oxidizing flame is a cool flame. It is a flame with a clear blue cone.  It will take you forever to fire a bead in this flame. 

Now turn knob to the left about one to two turns.  This is a neutral flame.  It should have a clearly defined inner blue cone with slightly bushy yellow edges.  This is the ideal flame … the one you're shooting for.  

Within the neutral flame, however, there is a reducing part of the flame, a neutral part of the flame, and an oxidizing part of the flame.  Remember, we're talking now about a flame that is set to the  perfect intensity.  Starting at the torch end,  you'll find the reducing flame.   If you move 2.5" to 3" from the torch end, you'll find the neutral flame.  Beyond the neutral flame is the oxidizing flame.  Each of these flames are useful to the torch-firing enamel artist. 

The neutral flame is where you'll find the "sweet spot".  It is where there is a near perfect balance of oxygen and fuel, which is what makes the flame hot AND clean.  This is the area with which you'll have the best relationship!  Bright colors are produced in a short amount of time.

So, when and why would we be interested in reducing and oxidizing flames? I primarily use the reducing flame to create special effects.  After I've fired the enamel to maturity (a glossy finish) in the sweet spot of the flame, I can finish the piece in the reducing flame to create a smokey haze.  Remember, the reducing flame contains non-combusted fuel. 

The oxidizing flame, which is beyond the sweet spot, is a great place for "flame annealing."  Flame annealing allows you to control how quickly the glass cools, which prevents thermal shock.  For a bead with a few layers of glass there isn't a need for controlled cooling.  However, controlled cooling is essential for enamel head pins. 

Use the flame to your advantage, whether you're firing enamel onto metal, getting special effects from a reducing flame, or annealing enamel head pins.  If you have any questions, please leave them in the comments section and I'll respond.  Have a great week!  Barbara

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