Hi Jenn, as stoneyboy says they could have been treated with almost anything over the years. If you find that the old colour bleeds through the primer/undercoat you could try using Aluminium Primer on it first then a white undercoat, oil or waterbased it won't matter after using the aluminium primer followed by a couple of coats of the emulsion with the rest of the ceiling. Dulux make this primer along with other companies so you shouldn't have any difficulty in buying it.
I have neglected to say that these beams are new wood put in a couple of years ago, standard interior stuff and not some ancient timbers.
Is the advice still the same?
Thanks very much for your thoughts
Hi Jenn, yes if you try what stoneyboy says and it does bleed through then try the aluminium primer on it and that should stop it. It really depends on what is on them to start with. There are a few other primers on the market that may also work but I find this one quite good on most things.