I change the font size in CALC but after saving and reopening the file they are lost. How can they be kept across saving and reopening?

Default font is 10 and changed to 11. Lost after saving and reopening file.

I am having similar problem, if I get answer I will update you. Did you by chance get a solution?

Which LibreOffice version are you using? I didn’t noticed that problem in 5.1.5.

And what file type do you use to save?

The file type is: XLS. I am using LibreOffice Version 5.2.0.4

I found a workaround.
Example:
If I want to change the font on 100 roes and have that saved across closes of the file, I put a “space bar” blank in the last row of the 100 and then select and change font. Not elegant but it does work.

I can’t say for sure, but to me it sounds like a bug. Which operating system? Does it happen every time and on new documents?

I discovered it under Windows Vista and currently I am running under Windows 10 and it is still happening.
Yes, it is happening on every new spreadsheet I create.

Well, If I were you, I would try to ask on LibreOffice’s users’ mailing list first. Maybe it should be reported to Bugzilla…

Bugs should be reported here: https://bugs.documentfoundation.org/enter_bug.cgi?product=LibreOffice
If you’re new to reporting bugs, this guided form is more suitable for you: https://bugs.documentfoundation.org/enter_bug.cgi?product=LibreOffice&format=guided