Unreadable Iced tea fonts on QHD display

On tumbleweed (plasma) Iced tea fonts are unreadably small, both in the control panel and more so for messages issued in web pages. Could anyone suggest how to fix this?
keywords: OpenJDK, Java, Scaling, hidpi, kde

I do not know anything specifically about Iced Tea, but for my high resolution laptop screen I have to set the screen display scale to about “2”.
In KDE Plasma 5
System Settings > Hardware > Display and Monitor Display Configuration
> Scale Display – there is a Scale slider.

A little dated but there are some still relevant tips for HDPI scaling in:
https://wiki.archlinux.org/index.php/HiDPI
including browser configuration.