# White under-base



## wiggle (Nov 7, 2008)

Is there any kind of trick to make your white under-base (on a dark shirt) a hair smaller than the actual image? I always have a problem registering my screens exact and get a little white on the borders of my multi-color prints.


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## S14Shirt (Nov 10, 2008)

Just scale it down. 99.9%


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## tdigital (Sep 14, 2008)

you need to choke the underbase a few pixels.. If it looks iffy on your positive, it'll be iffy on the press. In photoshop, you can select the underbase and contract a few pixels (depending on the resolution of the original file) to add choke.. 

OR you can spread your top images all equally.. you could also apply a slightly heavier ink deposit to your top layers to allow them to slightly spread on the edges due to dot gain.

Best way to fix it, it to try different things and see what's best/easiest/most efficient for you.


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## chuckh (Mar 22, 2008)

You really do not want to reduce the size of the image to create an underbase, ie. scale at 99.9% This would only work in an extremely few rare cases like a solid, filled in circle or regular geometric figure. Otherwise, you will not be able to register your images.

Preferably, add a 1 pt. white outline to your image to create a choke, or a 1 pt. black out line for your spread. Make sure your screens are tensioned to at least 25 newtons, preferably 30 or more, and make sure that they are within 1-2 newtons (Max) of each other.

Use as high a mesh count as you can, especially on the overprint, so that your shirt is not bullet proof. Good luck!


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## tdigital (Sep 14, 2008)

chuckh said:


> You really do not want to reduce the size of the image to create an underbase, ie. scale at 99.9% This would only work in an extremely few rare cases like a solid, filled in circle or regular geometric figure. Otherwise, you will not be able to register your images.


Isn't this the reason we use registration marks? This would make the use of a halftone underbase impossible based on what you've suggested.

This is normal and standard practice to my knowledge. How else would you print on black (aside from using a maxopake-type ink?)? 



chuckh said:


> Preferably, add a 1 pt. white outline to your image to create a choke, or a 1 pt. black out line for your spread.


The dpi used for the choke will be relative to the dpi of the image. 1pt may or may not be enough, hence the suggestion to use 99.9%, which is still subject to a case-by-case based on the image..


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## EastBayScreen (Mar 23, 2007)

As stated, scaling the underbase down will not work except on symmetrical 
shapes. (both horizontally and vertically symmetrical) Don't believe it? Take
the letter "A". Make a copy on a layer beneath it, scale it down, then try and
get them to line up.

Also stated, the correct way is to choke the underbase. 1 point is usually
sufficient. A point is always 1/72nd of an inch, and is completely independent
of image resolution.


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## tdigital (Sep 14, 2008)

EastBayScreen said:


> As stated, scaling the underbase down will not work except on symmetrical
> shapes. (both horizontally and vertically symmetrical) Don't believe it? Take
> the letter "A". Make a copy on a layer beneath it, scale it down, then try and
> get them to line up.


See attached  (They were all done by selecting the layer and using expand/contract.. I went crazy with the trapaholic image.. this is a manual way of adding a positive/negative stroke to anything be it geometrical or not)

In photoshop its "Select -> Modify -> Expand/Contract" depending on what you need..

You are correct about the pt thing though. I always manually decide how much trap/choke I want, but I will add that to the arsenal.


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## chuckh (Mar 22, 2008)

tdigital said:


> See attached  (They were all done by selecting the layer and using expand/contract.. I went crazy with the trapaholic image.. this is a manual way of adding a positive/negative stroke to anything be it geometrical or not)
> 
> In photoshop its "Select -> Modify -> Expand/Contract" depending on what you need..
> 
> You are correct about the pt thing though. I always manually decide how much trap/choke I want, but I will add that to the arsenal.



Good morning "tdigital"

When we did our seps using Photoshop, we followed the same procedure that you do. Note, however, that expand and contract do not scale the image. We now find it easier using Illustrator and adding the outline as I described. EastBayScreen uses the same example with the letter "A" that I use when I explain chokes and spreads. In any event, sharing thoughts and practices is what this forum is all about. Happy New Year to all!


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## tdigital (Sep 14, 2008)

good deal! Glad I could share something that might be useful. Scaling the image is definitely not the way to go. We got lost on translation there, but fortunately it doesn't take much time or effort to fire up illustrator or ps and create a picture that's worth a thousand words. 

The key is selecting the area/color range then doing the contract/expand. I don't think it gives you the option to use pt sizes which is why I didn't know about that 

And that's why this forum is great!


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## S14Shirt (Nov 10, 2008)

Sorry if I mis-informed anyone. I guess i'll have to give this a try. Thanks for clearing it up!


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## Texas Slick (Oct 30, 2008)

Howdy y'all
There's a post on here that shows you how to create a macro for Photoshop that will take an image and create an underbase for it. I can't find it right now but just do a search for white underbases and you should find it. It works great. Good luck


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## raw191 (Nov 16, 2008)

how do you decide what to underbase and what not to??


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## MVP J (Aug 29, 2007)

raw191 said:


> how do you decide what to underbase and what not to??


Glad someone beat me to it...also wondering the same thing. Let's say for example you were using a navy color ink on a red 50/50 t-shirt, would you use a white underbase?


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## Tj Ryonet Tech (Jul 28, 2008)

Underbases are usually used under light colors going on dark garments. That way you can maintain the color integrity on the dark fabric.


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## BP (Jun 10, 2008)

OLD SCHOOL! and it works. Back in the late 80's we used a pcs clear film in between the screen and the film when burning the screen. And it will still work to day!


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## amp267 (Oct 11, 2006)

BP said:


> OLD SCHOOL! and it works. Back in the late 80's we used a pcs clear film in between the screen and the film when burning the screen. And it will still work to day!


nice........have to try it sometime


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## eclectix (Nov 1, 2008)

THX a lot! Just started with Oki Laser Transfers (WOW 7.2) for my custom T-shirt printing in Amsterdam and needed this piece of information for my mask making! Now it seems to work out just perfectly!


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## alby (Nov 14, 2012)

wiggle said:


> Is there any kind of trick to make your white under-base (on a dark shirt) a hair smaller than the actual image? I always have a problem registering my screens exact and get a little white on the borders of my multi-color prints.


the best way
is to go to 
create the white spot chanel so that it is black then
filters/other/maximum
then set the number of pixels this will "choke" the white sep. ie. will take away this amount. If you add white etc can create other problems in the white channel
if you wan to add
then go 
filters/other/minimum
and set pixels.


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## Fuzzyfreak (Sep 24, 2013)

This is what it is all about here! Get it done and try to limit the choices a client has, not to get into the nest of evilness and debate. Traps work best in PS and add grow. Corellx6 and I'm sure previous versions are the same way, you need to use the outline tool. It all works simular to one another as far as programming goes.


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## sarvdeep73 (Nov 3, 2008)

What types of design are your printing? It is advisable to Choke Underbase by 1 point to avoid any outline orwhite coming out of design.


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## Ripcord (Sep 2, 2006)

I usually only underbase if white is one of the colors of the design. If it's a color on a dark shirt I use opaque ink and print/flash print, then flash and print a third time.

There would be no reason to underbase navy ink on any color shirt. (Well, maybe if the print is white and navy on a black shirt...) If the design is a combination of white and another color on a dark shirt, it would depend on what color the shirt and print are. Generally if the print color is darker than the shirt color I would not underbase it. If it's lighter than the shirt, most likely I would.

Every design and color combination is different, so there is no strict rule about how to do it. If your design has thin lines I would recommend spreading the overprint instead of choking the underbase. I use a 1.2 pt spread or choke.


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## alby (Nov 14, 2012)

Ripcord said:


> I usually only underbase if white is one of the colors of the design. If it's a color on a dark shirt I use opaque ink and print/flash print, then flash and print a third time.
> 
> There would be no reason to underbase navy ink on any color shirt. (Well, maybe if the print is white and navy on a black shirt...) If the design is a combination of white and another color on a dark shirt, it would depend on what color the shirt and print are. Generally if the print color is darker than the shirt color I would not underbase it. If it's lighter than the shirt, most likely I would.
> 
> Every design and color combination is different, so there is no strict rule about how to do it. If your design has thin lines I would recommend spreading the overprint instead of choking the underbase. I use a 1.2 pt spread or choke.


Thanks for the information. This job needs to be printed CMYK which, as you will know, are transparent so need the white underbase. Also there is a very bright green which process will not achieve it will need to be a spot. To get the brighness we need it will have to be on a white underbase.
We print all brights on darks on a white under base. Much chepaer doing it this way and you get a better, brighter, softer finish than trying to layup brights on darks in high cover inks.


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