set and keep default font in writer

When I set my default font and size in writer and then close it, then after re-opening and copy an article into it and saving it and closing. When I then re-open the file later, the default font size has changed back to factory default.
Assistance would be appreciated please.

Hello @sonata,

in Writer you can set the default font via the menu

"Tools : Options... : LibreOffice Writer : Basic Fonts (Western)"

Thank you for your answer. I have done this, but the problem is that when I re-open the article in Writer after having initially saving it, that is when the font size has changed back to factory default. That is, I set a default size of 10, but when re-opening it the default has changed to size 12. Kind regards, sonata.

Changing the default font (size) in Tools - Options only works in new documents. Existing documents aren’t affected. You wouldn’t want that, either. To change the font size in the default paragraph style, you have to modify that style. You can try if changing the font size in the default template works, but even then you will have to affirm that you want to update the styles in files based on that template.

Thank you floris v for your response.
I think that I may have muddied the waters a little. What I meant regarding the font size changing is:
After having created a new document with font size 10 and then saving it, when I re-open that same document a day or two later, the font size in that document has changed to size 12. That is what is puzzling me.
Thank you for your patience, kind regards, sonata.