White space in print
You will sometimes notice that the spacing between different aspects of your layout is not as consistent as you are used to. Or that there are fewer possibilities regarding line spacing than you had hoped. Why is there more white space between a paragraph and a figure on one page than on another? And why is it not possible to have a half line between paragraphs, but only a whole one?
This might seem inconsistent, but there are actually very logical reasons behind these seemingly strange spacings. They have to do with the grid on which lines of pages in books are situated. For every book, it is determined how many lines appear on a single page, as well as where they belong on the page. This is the grid, which is partly determined by the line spacing of the text.
This grid is very important. It ensures that when you turn a page of the book, the lines will always be in the same place as the lines on the previous page. If this is not the case, it creates a restless effect when you leaf through a book. This makes reading more tiring and makes your publication look messy.
What do figures, tables, or blank lines have to do with this?
Due to the grid, the height of a paragraph of text is always a multiple of the line spacing. The tricky thing about figures, tables, or blank lines is that they do not have a fixed height and can therefore end at a position that does not align with the grid. If you were to start a paragraph at this height, it would not fall within the grid and would be at a different height than on other pages.
To prevent this, a paragraph following a figure or table begins only at a location where it falls within the grid. This ensures the layout of the dissertation remains consistent throughout the entire book. The same applies to blank lines between paragraphs; here, too, the second paragraph can begin on the grid to prevent it from appearing at a different height.
Why does this look so weird then?
A grid on which elements in a book are aligned is the standard in print. Just open another book or dissertation, and you will see that white space differs there as well. The fact that you are only noticing this now is because, as readers, we look at text on a screen differently than at text on paper. On a screen, designers do not have to take a grid into account, because you do not flip between different pages, but simply scroll on. However, if you view a PDF of your dissertation, you are dealing with pages, despite the fact that it is on a screen. As soon as you see something on a screen that you normally view on paper, you notice things that you would otherwise take for granted.
The history
Apart from its contemporary function, the use of white space in print also has a historical reason. In the era of mechanical printing, lines of text were created by placing lead forms one below the other on a plate, a so-called galley.
As you can see, these lead forms had fixed sizes and positions on this galley. The line spacing and position were thus fixed; the original raster. Even though we are no longer bound by this limitation with contemporary digital printing forms, a fixed raster still proves to play an important role. If we were to print books in which we no longer apply it, it would be perceived as messy.
