The Spark Test and Spark Testing Metals

Ahhh, the allusive spark test. This indispensable tool/test in sorting metals/alloys has been used for at least the past few centuries, along with the magnet test. With the standardization of metals, it can be quite easy to distinguish many types of alloys just by looking at the stream of sparks they throw off (with a little practice of course)… Oh, and before starting the spark test, please be sure you have a large enough sample of metal. If it is so thin that it just melts, then you will not get an accurate spark stream. 

The first thing you want to do, is find a grinder of some kind. A bench grinder should be used, as apposed to an angle grinder or the like. Plus, I would rather hold the sample than hold the grinder, and that way I can get a nice steady stream of sparks due to control.

I tried writing out good description of the sparks of metal, but the truth is, this info graphic is 100x better than a written description. Here is this amazing pictorial I found in a very old magazine. Source

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The Spark Comparison:

The look of a spark is only useful if you know what it should look like!  That is why above the grinding wheel in my shop you will find a small fishing tackle box with small samples of different metals. In each compartment, I have different metals/alloys that I have come across in the past few years. (including a little Titanium).

All of these metals produce very different types of sparks that any shopman should become comfortable identifying. Ideally, everybody should have a small utility box of some sort in their shop or garage filled with samples of different types of labeled metals.

When you come across an alloy you need to identify, do a Magnet Test. That will narrow down many of the alloys in your box. Then, cross reference your sample's sparks with the sparks of your known metals.

In 1941, a Detroit Shopman spark tests automotive
metal stock for consistency.

Note worth characteristics:

• Number of Forks, Sprigs is proportional to the carbon content of the metal. The more carbon, the more of these bursts you will see at the end of the sparks
  
• Color is going to help identify the alloy content. The darkest red sparks will come from nickel, and cobalt, and tungston carbide
• Brilliantly WHITE sparks: Means TITANIUM! The most magnificent sparks I have ever seen are those from titanium. They are incredibly WHITE and luminous! 
• NO Sparks means that the metal is non-ferrous. This is particularly good for telling apart stainless steel from aluminum. 

Please remember, the more experience you have, the better you will be at identifying all types of metals. A little time invested in hitting a few different types of steel with a grinder, and you'll have a hold of it in no time.