The house is about 12 years old and the railing on the verandah has been painted about 3 times, but every time after around 6 months this blue starts to bleed through. Is it because the wood hasn't been treated correctly, or no sealer or undercoat before top coat. To take it back to bare wood and start again would be a big job, not one I wish to undertake.

Paint it blue, or a dark colour. 

Are you using any kind of sealer?

 

Have you been using lacquer or enamel? If you've been using lacquer and it fully cured you could scuff it and give it a coat of enamel.

1 hour ago, giddyup said:

The house is about 12 years old and the railing on the verandah has been painted about 3 times, but every time after around 6 months this blue starts to bleed through. Is it because the wood hasn't been treated correctly, or no sealer or undercoat before top coat. To take it back to bare wood and start again would be a big job, not one I wish to undertake.

Clean the paint throughly, lightly sand using about 120~180 grit, then use a good thickness of clear shellac, you can use almost any topcoat. 
 

The shellac is what is used to prevent bleed through of resins in wood knots and it can be used over any finish and any finish can go over it.

Shellac has saved me in the past - when my kid wrote on the wall with a marker.  It prevented bleed-through when using latex-based paint.  Also seals stains.

The house was previously owned by a US Democrat...will always bleed blue!  ????

9 hours ago, sometimewoodworker said:

Clean the paint throughly, lightly sand using about 120~180 grit, then use a good thickness of clear shellac, you can use almost any topcoat. 
 

The shellac is what is used to prevent bleed through of resins in wood knots and it can be used over any finish and any finish can go over it.

Which Shellac brand would you suggest, for sealing a bare wood door?

55 minutes ago, faraday said:

Which Shellac brand would you suggest, for sealing a bare wood door?

Any one will do, shark, whale,  crocodile, etc or you can buy flakes or powder and make up a ½ lb cut.

Grams	30
ml	500

this is the metric version.

 

The great thing is that for a sanding sealer, you do need to sand lightly, you can hardly go wrong. 
 

if you want to colour the door as well here is the crocodile colour chart. The colour charts are a little difficult to find and though the different brands have colours with the same name the actual colour is different. The bottles are 40~50 baht 

 

SWMBO decided that some draws I’m making from plywood need to be black so I’m using No8 diluted by 4 alcohol to 1 followed by No5 undiluted. I will then use an RTB water based poly to protect the surface. I am spraying the finishes because I have the equipment and the area to be covered is quite large at about 10 square metres. SWMBO has approved the colour so I need to go to buy more of the coloured shellac today.

 

13 hours ago, Yellowtail said:

Are you using any kind of sealer?

 

Have you been using lacquer or enamel? If you've been using lacquer and it fully cured you could scuff it and give it a coat of enamel.

Already painted with oil based gloss enamel.

13 hours ago, sometimewoodworker said:

Clean the paint throughly, lightly sand using about 120~180 grit, then use a good thickness of clear shellac, you can use almost any topcoat. 
 

The shellac is what is used to prevent bleed through of resins in wood knots and it can be used over any finish and any finish can go over it.

If I paint clear shellac over the top of the enamel won't the blue still be visible?

Just now, giddyup said:

If I paint clear shellac over the top of the enamel won't the blue still be visible?

Yes, but the shellac should seal it such that the it wont bleed through the next coat of enamel.

 

 

42 minutes ago, giddyup said:

If I paint clear shellac over the top of the enamel won't the blue still be visible?

Of course it will. It is clear. As I said.

 

14 hours ago, sometimewoodworker said:

you can use almost any topcoat. 
 

The shellac is what is used to prevent bleed through of resins in wood knots and it can be used over any finish and any finish can go over it.