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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.


6 thoughts on “Varnishing Over Paintwork”

  1. I have bought some American white oak veneer doors and the fitting instructions state that I cant use clear varnishes, waxes, polishes, oils or lacquers. I have been advised to use water based products but it is so confusing. The doors are interior with the exception of one exterior door, please can you advise me on what I should buy.

    • Veneered doors are often supplied pre-finished and some products will not be compatible with whatever finish they have used.

      For internal use a decent general purpose product Dulux Trade Quick Drying Varnish will do the job.

      Externally it isn’t so simple. There are water based varnishes available in the US where the climate is more suited to their use. The choice in the UK isn’t so great and most of the options available are semi-opaque colours (like paint), which is fine if that’s what you’re after?

      If you want a traditional varnish-like finish a coloured wood stain may suit? Sikkens Cetol BL21 is a water-based finish available in a range of natural wood shades. It’s water based and performs well externally.

      It would be advisable to paint a small area of the door (preferably on the edge) with your chosen finish just to test there are no compatibility issues first.

      • I have another question regarding my doors. I really want all the doors (interior and exterior) to match and in a satin finish, the same shade or colour so that when you walk in the front door it will match on the inside. My concern is that if we choose two different brands this wont be possible. Could I use the sikkens cetol bl21 plus on all the doors? I am assuming I wont be able to use the Dulux trade quick dry as its only for interior wood? if not can you suggest one product that will work for all my doors as in external and interior?

      • Yes you could use the exterior stain on all the doors. The only downside, apart from the extra cost, is that the exterior stain may dry with a flatter finish than you might like?

        One way around this would be to do all the the doors with the exterior stain and then do the internal doors again with the clear varnish. Then, although the sheen level will be slightly different, the overall colour will be the same throughout. So long as you allow plenty of time between each coat (at least 24 hours) I don’t envisage any compatibility issues with the 2 different products.

        Again, it’s advisable to do some small test areas first to ensure you’re going to be happy with the end result.

      • Hi Darren, thanks for coming back so quickly, much appreciated. It’s nice to get some proper advice from someone who really know’s what they are talking about. it’s certainly given us something to think about over the weekend. I will be able to spend some time now to make a more informed decision. I quite understand what you are saying regarding the higher cost of using the exterior stain on all of the doors (external and internal), but at least we will get a uniform colour throughout plus the internal doors will possibly have a better level of protection.
        Many thanks again

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