The traditional use of white ink has been to provide a base coat for colored inks.

The process inks are fairly transparent to allow better blending of colors, and to allow the whiteness of the stock to provide brightness, so even 100% of a process ink will let the color of the stock through (cyan, magenta, and yellow especially—Black not so much). So, if you are printing process color art onto fiberboard, you can expect a pretty big color shift and a darkening of the final product. Two hits (2x) White ink goes a long way toward bringing the level closer to white coated stock.

You're usually going to prefer the outcome if, instead of using a flood of white, you use it only behind the elements that need it, leaving the remainder the natural color.

Lots of really successful designs on fiberboard use the white ink as a stand-alone color.

Here's a sample of white inks printed on scrap fiberboard stock.

Are you are in love with the look and feel or fiberboard, but find that you are spending more time trying to overcome the strong color than you are doing anything else? If you find that you are fighting the fiberboard, you might want to Just try changing to an uncoated white stock. Some folks even print a fiberboard scan to get the vibe, without losing the white whites.

This project ultimately was done on coated white stock. The piece at the left was a press proof on fiberboard.

You certainly don't have to use spot white, and many projects really come to life without it.

On white paper, you get white "for free", but on brown paper, white is an additional color, and so does add cost. To do white on fiberboard stock, we use a special UV curing process. The drying time depends on how many coats of white are needed. Pricing is set for 1x and 2x coats of white.

Yes, although the Pantone inks are generally more opaque then the process inks, you might want to consider adding 2x spot white as a base—especially with the lighter colors. Even with 2x hits of white ink, though, you can expect some effect on color.

TO create artwork using white ink, you have a couple of options. You can create a spot color (spot channel in Photoshop) and set it to display as white. This may work fine for simpler files, but with Photoshop, it can be a headache to deal with. If you do use a custom color, make sure the name is the same in all files you are using, and try test separations on the art as a sanity check.

You can "theoretically" create a custom color, called "white Ink," and set its display color to white, and it will come out on its own plate in the separations.

Our preferred, but arguably old fashioned, method is to use a separate layer for your white, and make all "white" items there, filled and stroked (vector art terms!) with the same single process color. We will place the art you provide, and bring out the white layer to a different page of the layout, so that the areas to take white ink can be clearly seen.

Here are some pages that may help you with ideas:
Special Printing Effects
Hot Foil Stamping
Embossing and Debossing
Spot UV Gloss
How to set up Spot Colors
How to set up PIPS or reverse side printing
Custom Die Cuts
Unusual Folds and Shapes
Metallic Ink printing
Spot White Ink on Fiberboard Stock
Special Disc Printing
Uncoated Paper(Matte)
Fiberboard Paper (brown, kraft)

One of our favorite titles for show & tell is the Deva Film Reel as it actually has all of the effects; hot foil stamping, embossing and debossing, spot UV glass & lamination. Be sure to check our the full spec for the special printing effects on Deva's Featured TItle page.