Brick in the interior wall

[APKa]

We live in a brick house built in the 1930s with double-brick masonry. We are now renovating the interior, and on the exterior walls, a thin layer of plaster (about 0.5 cm) was applied to the brick, with wallpaper over it. We have removed the wallpaper, and in several places, the plaster has spontaneously fallen off, and in other areas, we notice that there are "hollow spots." This prompted us to remove all the plaster on one wall, revealing the brick. We are now wondering if the plaster has any insulating properties and should therefore be reapplied, or if we could clean the brick to create an attractive brick wall?
Grateful for answers.
Best regards,
Annika and Per

 

[Liteavvarje]

That plaster doesn't make a difference either way, it's up to you if you want a nice feature wall. There might be some mortar left on the stones (there are products to remove it), alternatively, you can leave it as it is, slightly mottled, or later apply paraffin oil (which neither smells nor smears and requires quite a bit in the first round, as the brick absorbs well). They will become darker and also mottled, and it needs to be redone sometimes (every 3-5 years). If you're thinking about oil, it can't be changed afterward. Otherwise, if you want wallpaper, attach boards before applying new wallpaper.

 

[APKa]

That plaster neither adds nor detracts, it's up to you if you want a nice accent wall. There might be some mortar left on the stones, (there are products to remove it), or you can leave it as it is, a bit mottled, or later apply paraffin oil (neither smells nor smears and quite a bit is used the first round, as the brick absorbs well) which will make them darker and also mottled, and it needs to be redone sometimes (3-5 years). If you think about oil, it can't be changed after, otherwise if you want wallpaper, put up sheets before new wallpaper

Thank you very much for the quick response.