I have to make a sticker for a pair of glass doors. It will be printed on vinyl and has to be translucent. Is there any specific process to incorporate the translucency? I've designed clear stickers before but I'm unsure about a translucent one. Do I reduce the opacity of the body or do I leave it for the printers?
The material itself is translucent. So you you need to visually/mentally factor that in when selecting colors to print. Think of it this way - if you print your solid blue on a clear plastic, an opaque white card, or a translucent vinyl - how that solid blue will look? It depends what that ink hits from medium to medium. The only way in my experience anything looks "solid" on a clear or translucent material is if spot white ink is additionally used. Have you read your product specs from the printer, or asked them?
1) Ask your PSP (Print Service Provider). Always ask them how they want this handled in special conditions such as these.
2) If only one element in your design is translucent - say a given field colour (fill inside a design element) but not say the primary linework - almost always the answer is that they have a specific spot ink callout they want used for the special translucent ink - if not, you choose a spot colour and designate it only for that translucent colour.
3) If the whole piece is translucent, I'd simply ask your PSP what colour system or even colour space they'd prefer you to use - they may have a specific set of Pantone Colours they prefer, or they may say "Oh, generic RGB" or even something highly specific to the colour profile of their given output device "Use Adobe RGB 1998" or "Use RGB Wide Gamut" or "CMYK - our machine has an in-line RIP we prefer to use, as designer's tools all seem to goof the colour when we let them go RGB"; they might even provide you a colour profile file to install and use - it's up to their process and their device.