Varnishing Over Paintwork

Question

i have a battered internal staircase (wood) in my 150 year old victorian house in dalston, london and i am in the process of trying to sort it out. i am not even going to attempt to replace the missing bullnoses, replace the treads which have been worn or even think about filling all the holes and cracks. rather, i have simply removed all the paint which either wanted to come off or needed a bit of help and applied multiple layers of undercoat. i will gloss them soon.

so i will gloss with dulux one coat but i want to add another layer for additional protection. ideally, i would simply buy these (http://www.stopslip.co.uk/anti-slip-products/anti-slip-treads/self-adhesive-stair-tread/non-abrasive/self-adhesive-aquasafe-clear-anti-slip-stair-tread.aspx), cut them to size and install on each tread. however, on those treads with the bullnose still there and those with pronounced wear there is a good chance that they will come off over time. not only can i see this happening but the company makes it clear the product is best for flat surfaces (the PVC or whatever it is will want to flatten over time because of its molecular structure) and their ‘conformable’ alternative should be used for surfaces which are not flat. only problem there is the conformable product is not clear / transparent and black would look a bit silly on a white staircase in a house.

so, after all that, my question to you would be can i varnish on top of the gloss and if so how long should i wait before doing so? i am not too concerned about yellowing over time as all oil paints start to go eventually but i would prefer a varnish that holds out as long as possible – can you recommend? lastly, i don’t really want to have to sand the gloss before applying the varnish (even though this would obviously make it bind better) as i will lose the gloss appearance then (sorry for stating the obvious!) and don’t want to add yet another step to the process.

answers on a postcard please…

thanks, Kieron

Answer

In theory, you can varnish over gloss; it’s what old-school coach painters and sign-writers would do to get a durable, high-gloss finish.

Now the problem is that because this isn’t something you’d normally do in a domestic situation I can’t give you an authoritative answer on what would be the best product to use.

There are many kinds of varnishes and lacquers available from spirit-based to cellulose which all dry very hard but are very likely to react adversely with a conventional gloss.

With domestic type products you basically have 3 choices (although there are many variants of each).

Traditional oil-based yacht varnish which should be compatible with most gloss finishes but it will yellow over time and can take some time to fully cure. So you wouldn’t be able to walk on it for a couple of weeks (ideally).

Then you have polyurethane varnishes which cure quicker but I’m not sure whether these would react badly with an oil-based gloss finish?

And finally, you have water based varnishes which are quick drying and, in theory, the safest option.

But, to reiterate, I can’t say what your best option would be? I would rely on good old trial and error, testing various combinations on a test area first but whether this is practical for you I wouldn’t know?

Second option is to get in touch with a traditional sign writer and ask for advice. Google is your friend here and there are still a few around.

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