|There are three layers of skin: Scaly layer, epidermis, and dermis. Tattoo machines are adjusted to penetrate into the dermis layer but NOT *through* it (below it is the fat layer of the body).
When the needles go into the sanitary tube they have a layer of ink on and between them. The needles make little holes in the skin, and the ink is deposited into the holes. This is why the skin has to be stretched so blobs of ink don't stay. Otherwise, the skin will latch onto the needles, grab the ink from them and generally make a mess.
The depth of a tattoo needle is very important element in the tattooing process. If the needle goes too far into the skin, it can spread ink under the skin and this is known as bleeding. For tattoo beginner’s, it is vital to know what the proper depth is. You must first be familiar with the layers of skin and how far into the skin you need to go. There are seven layers of skin, but only two that matter when tattooing; the epidermis and the dermis. The epidermis is the outer layer of skin, and the dermis is the layer of skin the tattoo needle should be injected into.
Know how far to go. The tattoo needles need to go between 1 and 2 mm into the skin in order to reach the dermis. If you go any farther than that, it can cause unnecessary pain to the person receiving the tattoo.
Set your needle. A tattoo needle needs to stick out of the machine tube about 1 mm to 2 mm. These measurements will vary from person to person, as everyone's body is different. Your needle and tube need to match.
Practice your depth. Before tattooing a person, it is recommended that you first test the depth of the needle on a piece of fruit. If the fruit becomes torn apart, you know your needle depth is too much. The same is true when tattooing a live person. If the needle depth is too much, there will be an excessive amount of blood coming back out of the holes the needle is making.
If the purpose is outlining, the depth should be about 1.2mm. If the purpose is shading, the needle should be set at 2.5 mm. You should practice by taking the machine apart and put it back together again until you can set up easy. This will get you used to visually gauging the depth and getting a feel for the machine.
It is good practice to open your new needle in front of the customer so they know it is new and sterilized.