Joining objects causes one to change materials??

I am trying to join multiple objects (ctr j) but the moment i do one the objects changes materials to something else completely. Is this a glitch?
I tried to google with no luck.
Here are before and after pictures in edit mode if that helps.
thanks for any info.


In your second screenshot the object does not have any material supplied so they are not changing materials if they didn’t have any to begin with

Ctrl+J joins selected objects to the currently Active object (last object selected) so the resulting object will have the modifiers of the active object. It can therefore be important to select objects in the right order. If the selected objects have their own modifiers which may need to be applied before joining (depends on your desired result)

Also it looks like you have some inverted normals (select all vertices and recalculate with Ctrl+N)

thank you.