MDF Varnish Problem





Results 1 to 20 of 20
  1. #1
    Join Date
    Sep 2006
    Location
    Gaborone, Botswana
    Age
    57
    Posts
    5,234
    Thanked: 1203

    Default MDF Varnish Problem

    Over the years I have varnished plenty of MDF board. Using from the cheap house brand varnish to Dulux Int/Ext varnish. Never had a problem.

    I now have this small desk tops I'm doing. I do the first layer and then let it dry/cure for a few days. The thin second layer then goes on. It is enough to give a decent gloss finish.

    I now experience this "wrinkles" on the surface. It is as if it was applied too thick and then it dries on the outside while still not cured below.

    What is happening here?

    EDIT: This was Fired Earth Velvet Wood from BW. The previous batch was done with Dulux Interior/Exterior Timbavarnish. The Dulux had worse results.
    Attached Images Attached Images  
    Last edited by KobusDJ; 2020/03/15 at 01:48 PM.
    Kobus

  2. #2
    Join Date
    Aug 2017
    Location
    Durban or Centurion
    Posts
    1,340
    Thanked: 1268

    Default Re: MDF Varnish Problem

    Are the two layers from different layers? Perhaps incompatible solvents in the mix?

  3. #3
    Join Date
    Sep 2006
    Location
    Gaborone, Botswana
    Age
    57
    Posts
    5,234
    Thanked: 1203

    Default Re: MDF Varnish Problem

    The 2 layers are always te same brand.
    Kobus

  4. #4
    Join Date
    Sep 2006
    Location
    Langebaan
    Age
    66
    Posts
    102
    Thanked: 45

    Default Re: MDF Varnish Problem

    MDF is very porous, but not consistently the same. I cannot really see the wrinkles, the darker spots may be denser, did not soak in as much as the surrounding material, more varnish (thicker) on top. Sand level and keep recoating with thin layers until all builds a thin glossy layer on top.

    M2cw

  5. #5
    Join Date
    Oct 2010
    Location
    Pretoria
    Age
    61
    Posts
    1,570
    Thanked: 522

    Default Re: MDF Varnish Problem

    Maybe the first coat had not cured properly, and the solvent in the second coat has softened the first coat again?

    Fibreglass gelcoat do exactly that when you apply a second coat if the first has not cured properly.

  6. The Following User Says Thank You to faniedup For This Useful Post:


  7. #6
    Join Date
    Mar 2012
    Location
    Randburg
    Age
    38
    Posts
    629
    Thanked: 1207

    Default Re: MDF Varnish Problem

    Canít see nicely but is it not that the mdf board is actually creating the wrinkles because itís porous and absorbing the moisture more in that area.

    Donít know if that makes sense. Maybe itís my eyes playing tricks on me.
    4.0 XJ Jeep Cherokee - Go anywhere
    Honda Civic Type R
    - Daily Drive
    Isuzu KB 250 Xrider - Swambo
    Grand Cherokee WK2 Hemi - Sold


  8. #7
    Join Date
    Jan 2013
    Location
    Friemersheim, Southern Cape
    Posts
    4,323
    Thanked: 3253

    Default Re: MDF Varnish Problem

    I have found MDF boards with 'harder'/more dense sections where absorption is different to other areas.

    Moisture also problematic but don't think in Gaborone an issue
    1998 Daihatsu Rocky 'The Kitty'
    2002 Daihatsu Rocky 'The Bully'

    "Socialism only works in two places: Heaven where they don't need it and hell where they already have it." -Ronald Reagan.

  9. #8
    Join Date
    May 2014
    Location
    Tshwanetoria
    Age
    67
    Posts
    1,964
    Thanked: 799

    Default Re: MDF Varnish Problem

    Is that the first or the second coat? The board is not darkened, so it looks like the first coat?

    If it is the first coat, then maybe something incompatible (such as silicon) was spilt on it?

    Did the wrinkled areas cured or are they still soft?
    Last edited by hatjohan; 2020/03/15 at 06:50 PM.



  10. #9
    Join Date
    Apr 2013
    Location
    Debbin
    Age
    38
    Posts
    339
    Thanked: 59

    Default Re: MDF Varnish Problem

    When say varnish, is it actual varnish, the turps based old school oily stuff, or some type of more modern Alkyd or Nitrocellulose based paint?

    if itís old style turps based oil varnish, over coating shouldnít be a issue if the 1st coat is properly dry, sometimes 2 days.

    with a NC based product you should be able to overcoat after just a few hours

    Alkyd based paints donít like to be overcoated and will almost definitely wrinkle

    also keep in mind that not all mdf is the same, some boards have more oil in it.
    some appear pink, some yellow, I think the pink is local, the yellow import.

    try with a nitrocellulose product. Plascon has Ss015 sealer which works well, then overcoat with a nitrocellulose gloss clear

  11. #10
    Join Date
    Sep 2006
    Location
    Gaborone, Botswana
    Age
    57
    Posts
    5,234
    Thanked: 1203

    Default Re: MDF Varnish Problem

    Quote Originally Posted by hatjohan View Post
    Is that the first or the second coat?
    It is a week after the second coat.

    This "wrinkles" only appeared a few days after the second coat was applied.
    Last edited by KobusDJ; 2020/03/15 at 09:37 PM.
    Kobus

  12. #11
    Join Date
    Sep 2006
    Location
    Gaborone, Botswana
    Age
    57
    Posts
    5,234
    Thanked: 1203

    Default Re: MDF Varnish Problem

    Quote Originally Posted by RvanZ View Post
    When say varnish, is it actual varnish, the turps based old school oily stuff, or some type of more modern Alkyd or Nitrocellulose based paint?
    It is the old school stuff. I mentioned the products in the first post.
    Kobus

  13. #12
    Join Date
    Nov 2011
    Location
    Cape Town
    Age
    52
    Posts
    1,527
    Thanked: 985

    Default Re: MDF Varnish Problem

    Quote Originally Posted by KobusDJ View Post
    It is a week after the second coat.

    This "wrinkles" only appeared a few days after the second coat was applied.
    What happened here-I'm fairly certain-is...

    The first coat penetrated into the MDF, and had a long time ( several days, you say) to dry.
    It dried with a few 'furred' patches/nibs, which did not allow varnish to form a full and complete 'seal' of the surface.

    On second coat, some of the varnish/solvent drew into the MDF at these areas -and the solvent migrated under the first coat adjacent to the incomplete seal, and allowed the first coat to soften and expand again and thus to form the wrinkling -I'm thinking!

    Some paints specify maximum overcoating times, as well as minimum, for this reason.
    Last edited by Patrick L; 2020/03/15 at 09:51 PM.
    "The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence."

    - Charles Bukowski

  14. #13
    Join Date
    Sep 2006
    Location
    Gaborone, Botswana
    Age
    57
    Posts
    5,234
    Thanked: 1203

    Default Re: MDF Varnish Problem

    Quote Originally Posted by Patrick L View Post
    What happened here-I'm fairly certain-is...

    Sounds possible BUT .... I have done literally hundreds of this over the last few years. Always using the same 2 coat method. Nothing has changed. It is the first time this happened.

    What is the chance that the MDF is to blame?

    .
    Last edited by KobusDJ; 2020/03/15 at 10:10 PM.
    Kobus

  15. #14
    Join Date
    Nov 2011
    Location
    Cape Town
    Age
    52
    Posts
    1,527
    Thanked: 985

    Default Re: MDF Varnish Problem

    Quote Originally Posted by KobusDJ View Post
    Sounds possible BUT .... I have done literally hundreds of this over the last few years. Always using the same 2 coat method. Nothing has changed. It is the first time this happened.

    What is the chance that the MDF is to blame?

    .
    I agree! it's the MDF to blame! -horrid stuff, really, in all respects of working with it, until finally finished and coated.

    It could be the cheap import MDF nowadays is not pressed as firmly and densely as before.

    Same with chipboard-
    when PG Bison were around, one could get premium quality chip/mdf/ ply/ osb at good price -nowadays it is mostly imported inferior stuff.

    Happy sanding!
    "The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence."

    - Charles Bukowski

  16. #15
    Join Date
    May 2014
    Location
    Tshwanetoria
    Age
    67
    Posts
    1,964
    Thanked: 799

    Default Re: MDF Varnish Problem

    How wide spread is the problem, only a few localized spots, or all over the board?
    Both side or only one side?
    Any chance that the board was contaminated after the first coat? From rat's pee to silicon spray and anything in between? Children in the vicinity that could have done that?

    Sorry for the many questions, but this is a strange phenomena that I have never encountered in my many years of doing the same. Unless consecutive thick coats are applied without observing the during times. But you first coat is hardly noticeable, so that is highly unlikely.



  17. #16
    Join Date
    Jun 2011
    Location
    Kempton Park
    Age
    65
    Posts
    1,678
    Thanked: 262

    Default Re: MDF Varnish Problem

    It is the wax used when manufacturing the MDF board. You get special undercoats for MDF.

    Technipaint: Elvolac make a good undercoat for MDF.



    I spray a lot of Mdf

    IT stops the edges absorbing spray paint as well.
    Last edited by Robbief; 2020/03/16 at 04:15 PM.
    Robbie
    Fortuner D4D
    Hilux 2.7 4x4 Raider.

  18. #17
    Join Date
    Sep 2006
    Location
    Gaborone, Botswana
    Age
    57
    Posts
    5,234
    Thanked: 1203

    Default Re: MDF Varnish Problem

    Quote Originally Posted by hatjohan View Post
    How wide spread is the problem, only a few localized spots, or all over the board?
    Not really wide spread. The desk tops are 650 x 500. The bad area in the first image is one of +- 120 x 80. 4 out of 36 boards have one bad area.

    Quote Originally Posted by hatjohan View Post
    Both side or only one side?
    The bottom only get one coat. See pic. The top side was like this before the second coat.

    Quote Originally Posted by hatjohan View Post
    Any chance that the board was contaminated after the first coat? From rat's pee to silicon spray and anything in between? Children in the vicinity that could have done that?
    No rats or children . I'm the only one around. Only some dust I get rid of with compressed air before I apply the second coat.
    Attached Images Attached Images  
    Kobus

  19. #18
    Join Date
    May 2014
    Location
    Tshwanetoria
    Age
    67
    Posts
    1,964
    Thanked: 799

    Default Re: MDF Varnish Problem

    Hallo Kobus. I am a bit stumped, so I will be giving my best shot. I forgive me if I do not express myself as best as I should, in the Inglish tale

    The random appearance as well as the geometry of the faults, makes me think that it is something that happened to the MDF before you received it - in other word some form of "contamination"
    Here I tend to agree with RobbieF that it could be the wax (lubricant) used during manufacture. Either a fault during the process where some was "spilled" by the machine, or insufficient sanding at the end of the process which is inter alia meant to remove such "spillages" (not all processes sand afterwards)
    Either way, when you applied the first coat, that coat was prevented from penetrating/bonding without you noticing is, due to the contamination.
    When you applied the second coat, that coat lifted the first coat and when it dried, it shrinked the first coat, hence that wrinkled appearance. The same effect you get when painting a newspaper. I think a final test for this theory would be to scratch off the problem varnish with your finger nail to see if there was any bonding of the first coat with the MDF.

    Have you sanded the MDF properly before applying the first coat? That would have removed any waxes, which by its nature, do not really penetrate. Speaking for myself, I wouldn't have done that, since MDF is mostly pretty smooth, and I would rather do that between coats.

    PS. Apart from the fact that I have some experience, none of books on the subject gives any other explanation than the ones mentioned earlier (layers too thick/insufficient curing time/ incompatible solvents/ surface contamination) Hence my fascination with your problem.

    Keep as posted!



  20. #19
    Join Date
    Dec 2014
    Location
    Cape Town
    Age
    54
    Posts
    3,053
    Thanked: 1918

    Default Re: MDF Varnish Problem

    Those mark look like smudges where something has rubbed against the board, either at the factory or at the retailer.
    Could have been something as innocent as chip fat off the worker's hands from lunch or a dirty glove etc.

    I have seen similar effects from painting metal that was contaminated with off-cut rags from the rag trade that were silicon treated in the cutting room.
    Cheers,
    John

    Rover P6
    Land Rover Discovery II Td5 Manual
    Range Rover P38 HSE
    Moto Guzzi LeMans
    Aprilia Tuono V2

  21. The Following User Says Thank You to JohnnoK For This Useful Post:


  22. #20
    Join Date
    Nov 2007
    Location
    Cape Town
    Age
    75
    Posts
    2,960
    Thanked: 1153

    Default Re: MDF Varnish Problem

    I am not an MDF user, but stumbled into this and thought some of you guys may find this Yank's painting of MDF interesting.

    https://www.youtube.com/watch?v=2BYdxSTgOkM

    Hier is 'n ander benadering:

    https://www.youtube.com/watch?v=YRPHjUt6Hww
    Last edited by Poen; 2020/03/17 at 11:08 AM. Reason: added a url
    *
    Youth is such a wonderful thing - what a pity it is being wasted on the young.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •