How to do trapping in Illustrator ?

[LovelyMaria]

hi guy's

long time, I really missed you guy's.

I have a Q I hope I will find the answer here ( as usual ), what I have is Illustrator file, 5 Color ( the fifth color is silver ) so black should be cutout in silver ( that is what the press man told me ), but he asked me to do him trapping also, My Q is, how can I do the trapping in the silver, using illustrator, cause I dont want to do trapping for each object separately, I want to do the trap in the silver ( which is back ground ) so it will be for all colors.
and what is the best hearline I have to gave for trapping ??

thanks in advance,
hope some one will understand me and gave an answer

[beermonster]

hi - i'll have a go!

ok - yes "cut out" or "knockout" as its known - you will need your attributes, stroke and colour palettes

select the black object and ensure in the attributes the "overprint fill" is UNCHECKED (so it cuts-out of the silver) - next you have a choice - you can chose to "spread" the black into the silver or spread the silver into the black (also known as a choke).

lets go with this - give the black object a stroke of black, in the stroke palette define the width of stroke - now this will be your trap and anything from a 0.2 to 0.4 will do - it's your call - but remember this:

the width of your trap is half of the stroke weight - so a 0.4 STROKE makes a 0.2 TRAP.

when you have applied the desired stroke weight, in the attributes palette ensure "overprint stroke" IS selected - and there's your trap.

if you know your desired stroke weights you can select by same fill colur and apply strokes to multiple elements at a go as well.

it's all done with overprinting strokes, so have a practise, and ensure you view with "OVERPRINT PREVIEW" so you can see your results.

occasionally you might have to draw some elements (placed images on spot colour backgrounds) so it's a good idea to have these on their own layer as well - it makes editing very easy.

have a go with a cyan box overlapping a yellow box and viewing with overprint preview. give the cyan box a cyan stroke and set it to overprint with a weight of about 5 point - so you can see how it works - zoom in and adjust the stroke weight to see your traps

i hope this helps - if i can help anymore - just ask :lol:

good luck

ps: there is an auto trap feature but I don't use this - the ability to control traps individually is more important to me than just saying "its trapped".

pps: with blacks, when you RIP the job and you have knocked out black from spot colours or silver, remember to NOT set "overprint black" in your print settings - this will undo all your hard work!