I have taken apart a pencil to get the graphite inside of it. My goal is to get it to glow red and be really hot. I am using a 31V 2.5A max power supply (an old printer charger). I am confident that it will work, but I am concerned about the safety. As long as there are no really bright arcs or anything, is there any danger? I head that they can emit harmful UV light. If it is not really bright but glowing red, is this a concern? Please let me know of any dangers.

 

As long as there are no really bright arcs or anything, is there any danger? I head that they can emit harmful UV light. If it is not really bright but glowing red, is this a concern? Please let me know of any dangers.

A carbon arc will emit copious amounts of UV radiation; a carbon rod glowing red due to resistive heating, however, will not.

Just take care you don't burn your house down.

 

So there are absolutely no dangers if it is not really bright, aside from the extreme heat? Also, how would you block the UV radiation so that it is not a danger if you wanted to make arcs but be safe?

 

So there are absolutely no dangers if it is not really bright, aside from the extreme heat? Also, how would you block the UV radiation so that it is not a danger if you wanted to make arcs but be safe?

Ordinary glass is opaque to the most harmful spectrum of UV radiation. But to generate an arc, you normally require voltages much higher than the 31V you've just mentioned... in the order of several thousand, as a matter of fact.

 

So regular glass glasses are enough? I thought you needed special welding glasses to filter all the harmful light out.

 

Also, not really a high voltage arc, but one like in this video:

 

So regular glass glasses are enough? I thought you needed special welding glasses to filter all the harmful light out.

Oh yes... I was only talking about the UV radiation. But an intense graphite white-light arc emits light in all the visible spectrum, as well as IR and UV. As a matter of fact, they also emit radio frequencies, and are banned by the FCC for use as a source of illumination due to their jamming effect on communications.

So yes, treat such arc just as you treat a welder's arc, using appropriate filtering glass.

 

Where could I get such filtering glass? And is it necessary if it is not making bright arcs, but being used as a resistor? I just want to make sure I am aware of all the dangers and can prevent any possible harm.

 

Where could I get such filtering glass?

An ordinary welder's helmet would help you out. Amazon sells them real cheap:

https://www.amazon.com/Hobart-770286-Front-Welding-Helmet/dp/B00024Z37E

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Cheap and good? I want to make sure it will work for my purposes and filter everything that needs to be filtered out.

 

Ordinary glass is opaque to the most harmful spectrum of UV radiation. But to generate an arc, you normally require voltages much higher than the 31V you've just mentioned... in the order of several thousand, as a matter of fact.

When I was a kid--early 40's?--I got arc lights with my mother's iron as a ballast and two carbon rods from D cells. I'm lucky to have survived childhood.

 

Cheap and good? I want to make sure it will work for my purposes and filter everything that needs to be filtered out.

Yeap... it's cheap and good... and most importantly, safe. At least for your face and eyesight... but be very extra absolutely careful if you're planning on experimenting with high voltages... I can't stress that enough.

 

When I was a kid--early 40's?--I got arc lights with my mother's iron as a ballast and two carbon rods from D cells. I'm lucky to have survived childhood.

... I hope you didn't have to use a Braille keyboard to type that last post ...

 

There are no high voltages involved. Just the 31V from the power supply.

 

There are no high voltages involved. Just the 31V from the power supply.

I very much doubt you'll get a continuous arc out of that... just a few sparks when you rub both terminals together.

 

I will measure the current when it is being used just as a resistor, and it might be enough.

 

I will measure the current when it is being used just as a resistor, and it might be enough.

graphite is highly conductive... you might blow a fuse in your power supply, or worse.

 

There is a circuit breaker that triggers when there is a lot of overcurrent for a second or two. You have to unplug and replug it to get it to work.

 

When I was a kid--early 40's?--I got arc lights with my mother's iron as a ballast and two carbon rods from D cells. I'm lucky to have survived childhood.

I had all but forgotten taking apart D cells (late 1950s) that were dead and removing the carbon rods and building carbon arc lamps. Yeah, more than once I have looked back and wondered why I survived those formative years.

My friends father had a print shop and the rage was an AB Dick 360 offset press. The plates were burned using huge carbon arc lamps. Serious bright stuff. Safety glasses what?

Ron

 

Anyways, given the dangers, I think I am just going to heat it up and have it glow red and avoid arcs.