My problem is that the font seems to change when I change it's size with \fontsize .

I am trying to adjust the size of a font within an acm template author block. I'm using the code from this post to print out the font info.

When I print out the font info before changing anything I get the first line. Then I call

\fontsize{13 pt}{1 em} \selectfont

and I get the second line. Finally I tried to change the family with

\fontsize{13 pt}{1 em}\sffamily \selectfont`

and I get the third line which kind of looks right but seems to be magnified rather than a real font size and is also clearly a different family from the other two.

Edit: While creating a MWE I discovered it's some weirdness with the acm cls file.

The example is: