Step 4 – Creating trap between layers
Trapping when screen printing will reduce the chances of there being gaps between the colours or outline, so is an essential part of the screen printing process. Not to say some small gaps give your design a little artistic flair.
Adding trap to your colour layers first and then your top layer / outline if needed (it’s not always essential for your outline to have trap applied). You may want to either hide your black / outline or put it to the bottom of the list of layers for this part of the process to make it easier to see what parts of your design have the trap added.
Ways to add trap to design for screen printing
This can be done by adding a small amount of stroke either in MM or PT depending on how you set up your artwork.
Another method is to use the offset path feature in illustrator by going to: Object > Path > Offset Path.
You want to play around with the settings:
- You only need a small amount like 1 mm max
- Set “Joins” to “Mitre” which is a little more accurate than over methods
- “Mitre” limit set to 4
- Tick preview and it will show the changes live on screen
Make sure to check the layers to see if any parts that have had trap added are inline. Some parts may bulge out, you can either move your anchor points or use the pen tool (N) and draw across the bulging part. Just make sure each layer you add trap to is nice and tidy, you don’t want excessive parts of the light layer printed under your dark layer as it can mute the darker colour.
Checking the trap layers together
You can check the trap on each layer by making the top layer’s opacity lower, this will show the layer below and how much the top layer (low opacity) overlaps. You can lower the opacity of each layer by varying amounts to see them overlaid on top of each other.
The way to change opacity of colours in illustrator is: Window > Appearance > New Window Bottom Right > Opacity > Edit As Needed
If the colours meet, A good rule of thumb is to have your dark layer overlap your lighter layers when planning, in other words make sure the dark colours slightly overlap the lighter colours.
Make sure to check these layers well before the next step and make sure there are no gaps in your print. Make sure to reset the opacity after this step.
Also if you use illustrator you can hover on the paths and it will highlight the path line to show through the top layers.