varnish to sanded desk top

[wbmkk]

My daughter asked me to sand an old desk top which had a few scratches on it.

Now I have to varnish it and was wondering whether I should use an oil based varnish or a water based one.

By the way is varnish just another word for polyurethane ?

How many coats would you recommend please too ?

 

[KenGMac]

wbmkk, good evening.

My preference would be to use a so called "Yacht varnish"

As I understand it, water based varnish WILL dis-colour and mark if any liquid is spilled on to the surface of the water based varnish, such as water rings from the base of a cup or tumbler.

I believe that Yacht varnish is on of the tougher, and more expensive types on the market, as for cost because you are covering a relatively small desk it should be an acceptable expenditure?

As for number of coats? suggest three, with very, very light sanding with a very, very fine sandpaper between coats.

Ken.

 

[Doggit]

I think polyurethane is a water based varnish, whereas yacht varnish is solvent based, and much more resistant to knocks. I'd go for 1200 grade wet and dry between coats to get a really good finish, or wax and wire wool if I remember my woodworking classes at school, and as Ken suggests, at least 3 coats as you'll be taking off at least one of them in the sanding process.

 

[endecotp]

I did my desk with a hard wax oil. It is much more forgiving than varnish, i.e. no visible brush strokes, and seems to be hard wearing.
Read the instructions and do a test on a bit of scrap wood first.

 

[Doggit]

Thanks for that tip Endecote, that would have been a lot easier than the teak oil I used recently on an Oak worktop. I've still got one more to do, so much appreciated

 

[chappers]

don't use wire wool on oak though.
Yeah teak and Danish oils can take loads of coats to finally reach a level whereby you actually have a durable surface, especially in Oak with just eats it up, not so bad on say beech.
Hard wax oils are my preference for worktops , with Junkers rustic oil being by favourite

 

[Doggit]

don't use wire wool on oak though

Out of interest, why not.

 

[JohnD]

ordinary wire wool is steel, and tiny particles will cause iron:tannin staining in various timbers, but especially oak. Steel and iron nails and screws are traditionally not used in oak for this reason, only brass. Stainless steel is said not to have this problem, but I haven't tried it.

(wire wool particles can also cause staining in other materials if they become embedded and later rust due to damp)

 

[chappers]

yep even be careful with the tools you use. A few years ago, even being aware of the problems of iron with oak, I was filling some shakes and cracks in some raw oak floorboards with a mixture of PVA and sanding dust, with a cheap steel filling knife and within a week all the filling had turned black. even the iron in the haemoglobin in your blood will stain oak black if you bleed on it.

 

[JohnD]

Oxalic acid will bleach it temporarily, but I think it will return if it gets damp. I think it might be in rhubarb leaves.

Used to have some premises with an old oak door, it was very dark, so stains from hinges and lock might not have shown.

 

[Doggit]

Well I shan't be checking that one out, that's for certain