Colouring Pine

[stan250]

If you are spraying it then you will have to do it outside.
The reason I say keep things warm is that it helps get a good finnish.
Cold conditions will cloud the finnish and make it patchy. Will be less of a problem with low sheen.
Just pick a warm day that is still no wind to blow dust around .
Only thin it down just enough to spray correctly. If you thin it too much you will get runs of the edges and drying time may be affected . Try it unthinned first on some scrap and go from there.
Only thin with the solvents recommended on the can. From memory Carbothane is turps based.
I have never had a problem with water staining the wood with carbothane .
Several thin coats is usually better than one thick coat because it can be put on flatter which requires far less sanding ( steel wooling) between coats . When you steel wool it don't use your fingertips it will leave hollows. Use the flat of your hand with a big flat pad of steel wool. Watch the surface it will go a milky white colour to indicate you have done enough and move on.
Go gentle you should constantly feel with your other hand when it smooths up and thats enough.
Put on a light coat and let it dry properly then gently smooth it off with the steel wool , dust it up and start again . After a few coats it should start looking flat and even . Don't steel wool the last final coat .
If you have never done this kind of work before it would be a good thing to practise the whole job on a piece pine first to get the whole idea in your head and see what kind of finnish comes up. Once you get the hang of it , it will give you confidence to tackle the main job. That is what I allways do even today and I have made a thousand billiard and snooker tables in my time.
Products change all the time and a bit of practise can do wonders for the final job.
Another thing that may have been a problem is that you must use a water based stain with a water based varnish and a spirit stain with a turps based varnish.

thanks for all that- I appreciate your help with this.
To prevent cupping do I need to give the underside as many coats as the top or will one or two do and in fact how many coats is needed on the top to give a kitchen worktop proper protection, do you think?

[Retromilling]

It is a good idea to seal all around for sure especially in a kitchen situation . two coats on the bottom should seal it up ok or if you like put the same on as the top but dont bother with the steel wooling on the back.
If the top is not a laminated design (lotts of strips glued together ) then it would be a good idea to glue some cleats accross underneath in a few places where they will not get in the way of fixing it in place , just to resist any tendency to warp as pine can warp all on its own.
How many coats it takes is hard to say depends on how thick each coat is applied and how absorbant the wood is , how much you cut back . I use a sanding sealer first which cuts down on the need for extra top coats its like using a primer in normal painting .
I think by three maybe four coats should bring up a nice even well sealed surface.
You just got to be guided by what is happening on the job surface. If you get to the third coat and it looks good and is nicely sealed then that is ok. If it still looks a bit uneven and not sealed then keep going.

[Harry72]

If you are spraying poly do not spray it outside!!!
Poly is a slow drying finish, its exposed to dust and crap(insects love it) for a longer time and can not be repaired without a fair amount of work(and waiting several days for it to cure fully first, with the exception of denibing).

I do it differently to RetroM, I dont bother with sanding sealer as polyU is its own sealer... poly sticks to fresh poly very well.(after several weeks it does not, it must be keyed by sanding)

1st coat goes on thinned out 20~50% this acts as the sealer, if the grain has raised or a lot of dust has settled a very light sand with 220grit+, if not dont bother with sanding it.

2nd coat thin by 10~15% and flood it on(within reason!), you'll find polyU works just like enamel car paint if you put it on thin it will not level out and look crap(with spraying and brushing, rubbing on is different).
Once again if its rough with dust a very light sand with 320g+ or steelwool it over just enough to remove the inclusions.

3rd coat is a repeat of the 2nd.

A few hints
PolyU flows out so put it on thick

Runs can be repaired by letting it cure for at least 48hrs in hot weather(longer in cold), then wet rub it back flat using a dash of detergent in the water, you must then recoat it.

Cheap poly and turps= cheap die in 2 yrs finish

Never ever overwork/overspray it(like enamel), after 2~3 minutes do not go back over what you've already coated, if brushing it will leave very ugly brush marks... if spraying it may orange peel(dimples due to surface tensions).

1 seal coat and 2 top coats is plenty, it should be .5~1mm thick!

[Retromilling]

If you are spraying poly do not spray it outside!!!
Poly is a slow drying finish, its exposed to dust and crap(insects love it) for a longer time and can not be repaired without a fair amount of work(and waiting several days for it to cure fully first, with the exception of denibing).

I do it differently to RetroM, I dont bother with sanding sealer as polyU is its own sealer... poly sticks to fresh poly very well.(after several weeks it does not, it must be keyed by sanding)

1st coat goes on thinned out 20~50% this acts as the sealer, if the grain has raised or a lot of dust has settled a very light sand with 220grit+, if not dont bother with sanding it.

2nd coat thin by 10~15% and flood it on(within reason!), you'll find polyU works just like enamel car paint if you put it on thin it will not level out and look crap(with spraying and brushing, rubbing on is different).
Once again if its rough with dust a very light sand with 320g+ or steelwool it over just enough to remove the inclusions.

3rd coat is a repeat of the 2nd.

A few hints
PolyU flows out so put it on thick

Runs can be repaired by letting it cure for at least 48hrs in hot weather(longer in cold), then wet rub it back flat using a dash of detergent in the water, you must then recoat it.

Cheap poly and turps= cheap die in 2 yrs finish

Never ever overwork/overspray it(like enamel), after 2~3 minutes do not go back over what you've already coated, if brushing it will leave very ugly brush marks... if spraying it may orange peel(dimples due to surface tensions).

1 seal coat and 2 top coats is plenty, it should be .5~1mm thick!

I did not mean he should use sanding sealer and carbothane will dry within hours to resist dust and insects.
It would be better to do it indoors but he has said he can't.

[Harry72]

RM I meant to reinforce what you said about using poly outside, sorry if it didnt come out that way
Yes Carbothane is touch dry in 1~2hrs but thats a long time when dust and insects are concerned.

[Retromilling]

RM I meant to reinforce what you said about using poly outside, sorry if it didnt come out that way
Yes Carbothane is touch dry in 1~2hrs but thats a long time when dust and insects are concerned.

True , it can be a problem especially on the final coat .