slow blue

Slow rust blue and
Pattern damascus blue

Slow rust bluing dates to the earliest forms of bluing, and is still used in many high end custom built guns.

Early double barrels used soft lead solder to join the barrels and center ribs, which wont stand up to the chemicals of the hot blue process so finding someone who can slow rust blue is the only way to get these re-blued.

Damascus barrels fall into this category, and uses the same process with a few added steps to get the full pattern of the hammer welded bands to be visible.
Many of the higher end guns even have purposely wrought designs in the patterns like chain link.

Here is one example of slow rust blue in a deep black shade.

Another set showing a lighter deep grey tone.

The two side by side for comparison.

Here is an example of pattern bluing on damascus.This finish is done in much the same way as the slow rust blue, but takes considerably longer to complete.

Please understand, that the color shades may vary on different barrels depending on the carbon content in the steel used in its construction.
Here are two other examples.

The same set run to a darker hue.

A "before" shot

After being re-finished

Again what we started with.

The nicely figured rib was a surprise bonus!

Here is a set done in a more traditional brown/white.

Damascus Blue

The fairly common style of doing pattern bluing is similar to this grey/white example.

The steps and variations in rust blue.

Another good use of rust blue is shown here.
In the first pic, you can see the common result of hot blue on hardened steel parts.
Notice it is more a purple color like steel that has been heated with a torch.

here is the same part after rust bluing.
A much more acceptable look that will blend closer to the rest of the blue on the gun.