1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Patchy painted wood? (waterbased undercoat and satin topcoat)

Discussion in 'Decorating and Painting' started by zenonithus, 21 Sep 2018.

  1. zenonithus

    zenonithus

    Joined:
    15 May 2016
    Messages:
    289
    Thanks Received:
    2
    Country:
    United Kingdom
    Hi all,

    My dad painted the wood in the hallway. On some of the architrave I noticed areas were uneven with dark patches. I applied more topcoat (satinwood) though when it dried it was still a bit patchy. I can only assume he may have watered down the undercoat too much and applied the topcoat when the undercoat still looked pretty washy and not 100% opaque. Shall I just add more satin wood coats or would it be best to add a layer of undercoat on the patchy areas then paint over again with topcoat?

    DSC_0311.JPG
     
  2. footprints

    footprints

    Joined:
    21 Sep 2011
    Messages:
    3,780
    Thanks Received:
    712
    Country:
    United Kingdom
    Might be better using more undercoat it is less translucent that top coat and it is only a small area if its just a door frame to redo, then two top coats. He may have been painting over patches of that horrible brown varnish all paintwork was finished with in pre war houses, or knots in the timber.;)
     
  3. zenonithus

    zenonithus

    Joined:
    15 May 2016
    Messages:
    289
    Thanks Received:
    2
    Country:
    United Kingdom
    Good suggestion, will do that. Will the undercoat adhear to the topcoat ok? The wood was dipped and stripped though some areas are still a bit sticky after a year. Might have to bin primer those.
     
  4. footprints

    footprints

    Joined:
    21 Sep 2011
    Messages:
    3,780
    Thanks Received:
    712
    Country:
    United Kingdom
    If you have BIN do the whole frame, dipped and stripped will have exposed the knots again BIN will seal them well it is very similar to knotting but in my opinion better.(y)
     
  5. opps

    opps

    Joined:
    16 Jun 2006
    Messages:
    3,668
    Thanks Received:
    510
    Location:
    London
    Country:
    United Kingdom
    You dipped door frames (or is it a window)?

    As much as I like BIN, it is impossible to apply it to a high standard by brush over larger areas. It dries too fast.

    It is also extremely hard and thus difficult to sand flat. Great as a spot primer though.

    If you do decide to recoat everything with BIN, then buy a bottle of household ammonia. BIN is pigmented shellac suspended in alcohol (hence as Footprints alluded, it helps to seal knots). The ammonia, being alkali based will break the BIN down on the brush, unlike meths which simply dilutes it. Even if your brush goes stiff the ammonia will make it good as new.
     
  6. footprints

    footprints

    Joined:
    21 Sep 2011
    Messages:
    3,780
    Thanks Received:
    712
    Country:
    United Kingdom
    Good tip about the ammonia I will give that a try next time(y) As said you need to work fast, a frame should be OK but never try it on a large area like a door!;)
     
  7. opps

    opps

    Joined:
    16 Jun 2006
    Messages:
    3,668
    Thanks Received:
    510
    Location:
    London
    Country:
    United Kingdom
    The ammonia is brilliant.

    Leave the brush to soak overnight (if hardened), preferably outside given the smell. The next day, the ammonia will have evaporated off. You will be left with water and the dusty pigment at the bottom. You can pour it down the sink and nothing will cling to the sink as you do so.

    Since I discovered the benefits of using ammonia, I am happy to use my Purdy brushes/rollers rather than cheapo throw away brushes/rollers.

    I would add that foam rollers will expand to more than twice their length and eventually fall apart if you try to use them with BIN.

    Should you ever need to thin BIN, use alcohol, eg isopropyl alcohol.

    Years ago, when I was cabinet painting, as an experiment I tried using vodka with BIN. It helped a bit but using BIN as an MDF primer added 50%-80% longer to the whole job once I sanded it back (compared to standard ((grain raising)) waterbased primer).
     
    • Like Like x 1
  8. zenonithus

    zenonithus

    Joined:
    15 May 2016
    Messages:
    289
    Thanks Received:
    2
    Country:
    United Kingdom
    Cool! Some good tips there oops. I used methelated spirits to work with the Bin as it is indeed very difficult to work with as it drys so quick. I will try the amonia to clean my brushes as that seems to work a treat. I have a large bottle of IPA so good to know I can use that to thin as methelated spirits don't come cheap ;)

    So is it ok to just use undercoat on bare wood or do you need to primer first? Especially if the wood has been dipped? I was going to primer the doors with BIN though might be difficult to work with.
     
  9. opps

    opps

    Joined:
    16 Jun 2006
    Messages:
    3,668
    Thanks Received:
    510
    Location:
    London
    Country:
    United Kingdom
    If the wood has had a caustic soda dip, the firm undertaking the dipping normally applies a neutralising agent after.

    As footprint says, any knots should be treated with shellac (BIN will suffice).

    The wood will need priming, however, waterbased undercoats (unless otherwise specified) are primer/undercoats. You shouldn't just put oil based undercoat over bare wood. BIN is OK as an interior wood primer, and as a exterior spot primer for woodwork.

    You can buy BIN in spray cans but in my experience it clogs the nozzle pretty quickly and spits a lot.

    BIN can be rolled with these Purdy mini roller sleeves but the sleeves will only fit the Purdy and Wooster (birdcage) mini rollers.
     
  10. zenonithus

    zenonithus

    Joined:
    15 May 2016
    Messages:
    289
    Thanks Received:
    2
    Country:
    United Kingdom
    OK great. I was using white foam rollers with bin though they seemed to disintegrate after a short while and bits of foam all over the paint so will try the small purdy. One problem I have with painting the doors with the undercoat is they go slightly yellow in areas. Also some areas go a bit cakey and the paint doesn't sit right. Not sure if those are sticky areas. Was thinking giving the doors a quick coat of bin will hopefully prevent all these issues.
     
  11. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page