Blotchiness and working with wood — K2Forums.com

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Blotchiness and working with wood

Hey Everyone, and thanks for having me.

I'm posting pictures of my 2nd attempt at dipping MDF. I did a few coats of OHW black beforehand. I'm guessing the blotches are from the MDF not being completely sealed by the OHW, and absorbing the film ink. I realize MDF is very absorbent.

My question is, what's your favorite way to seal wood prior to dipping? I do a lot of fiberglassing, so I was thinking maybe a coat of fiberglass resin, but that's going to go on thick and require some sanding afterwards to level out, so a spray would be preferable. Looking forward to any tricks you guys have. Thanks!

-Chris




Comments

  • MidOhioHydrographicsMidOhioHydrographics Posts: 8,516Member, Moderator, Business Ninja El Moderator
    Spray a bunch of coats of Helsman spar Urethane Aerosol, sand, and then paint to the sealant. A good 2k epoxy primer would work also.
  • norcalfranknorcalfrank Posts: 776Member ✭✭✭
    What @MidOhioHydrographics said. This was recomended to me here and I have used the Helmsman successfully on wood rifle and shotgun stocks.
  • studebakerstudebaker Posts: 2,616Member, Business Ninja ✭✭✭✭✭
    An alternative method would be to thin your mixed resin with styrene and brush it on in several coats. It will soak right into the MDF on the first coat. The second coat will seal it.
  • WileECoyoteWileECoyote Posts: 5,488Member, Moderator, Business Ninja El Moderator
    search bar has discussed sealing wood and Helmsman spar urethane at least a few dozen times
  • schidroschidro Posts: 286Member ✭✭✭
    Any time we did any painting on speaker boxes we always sprayed a coat of high build primer, let that soak in then spray another coat then sand. Then paint to perfection. 
  • DrunktankDrunktank Posts: 5Member
    Thanks guys. The Helsman worked great, and the dip went well. The only problem is one line of what I'm guessing is overactivation holes. I assume this happened when one of the passes of activator overlapped the previous pass, overactivating that one thin strip. Is that a possibility?
  • IceMasterIceMaster Posts: 1,150Member ✭✭✭✭
    @Drunktank, are you sure it's not a line of "holes" due to trapped air when you dipped? Show a pic and we can help more
  • DeviousDipsDeviousDips Posts: 1,014Member ✭✭✭✭
    I agree if it is a line of holes you prolly dipped it to flat. Was the holes at the point of entry
  • K2ConceptsK2Concepts Posts: 12,198Administrator El Jefe
    I would never enter this title in a Google search...just saying...
  • DrunktankDrunktank Posts: 5Member
    Yes, no image searches for this thread title

    Thanks, I'll take a picture when I get home. As you can see from the first picture, it's a very flat piece, I don't *think* there's anywhere for air to get trapped.

    You're right DD, I probably only dipped it at like 20 degrees because of the 45 degree edges of the piece. I figured I want to give that trailing 45' edge a chance to go down into the ink instead of going straight vertically down, if that makes sense. In other words, if a piece has a 45 degree edge all the way around it (as seen in the 2nd picture), then if I dip at 45', the leading edge will be parallel with the water, and trailing edge will enter the water vertically. Is that trailing edge going to pull the ink to it as it goes in instead of the edge coming to the ink? Anyway, that's why I'm dipping at shallow angles.
  • WileECoyoteWileECoyote Posts: 5,488Member, Moderator, Business Ninja El Moderator
    "Line of holes" has some cautions against it as well...
  • NotSoFastNotSoFast Posts: 3,059Member, Moderator El Moderator
    Drunktank said:

    Yes, no image searches for this thread title

    Thanks, I'll take a picture when I get home. As you can see from the first picture, it's a very flat piece, I don't *think* there's anywhere for air to get trapped.

    You're right DD, I probably only dipped it at like 20 degrees because of the 45 degree edges of the piece. I figured I want to give that trailing 45' edge a chance to go down into the ink instead of going straight vertically down, if that makes sense. In other words, if a piece has a 45 degree edge all the way around it (as seen in the 2nd picture), then if I dip at 45', the leading edge will be parallel with the water, and trailing edge will enter the water vertically. Is that trailing edge going to pull the ink to it as it goes in instead of the edge coming to the ink? Anyway, that's why I'm dipping at shallow angles.

    You can trap air on a completely flat piece if you first hit the water too flat. Fill a bowl with water and slowly dip a clear piece of glass perfectly flat to the surface. The under side will be covered with bubbles.

    Also make sure all trailing edges are back taped. Take some masking tape and put half the width on the back of the part and let the other half hang off the edge. This lets the film flow off the part and not tear along the edges.
  • DrunktankDrunktank Posts: 5Member
    Here's the picture I'm talking about. Just seem to be a vertical line of overactivation. Don't worry about the smudge in the bottom right, that's just my camera. Thanks as always!

    image



  • WileECoyoteWileECoyote Posts: 5,488Member, Moderator, Business Ninja El Moderator
    Honestly, there are so many underactivation spots on there, its hard to see what you think might be overactivation. OVER activation presents itself as an "oil and water" look. the ones you see in a straight line may very well be bubbles, but the ones on the left in the middle are CLEARLY underactivation. Stop worrying about overactivation and get some more material on that film.
  • NotSoFastNotSoFast Posts: 3,059Member, Moderator El Moderator
    Agreed. There is no over activation in that picture.
  • DrunktankDrunktank Posts: 5Member
    Well crap. I thought under looked more jagged like the ink never stuck and over was round and smooth like the hole melted into the ink.

    Anyway, I'll spray the heck out of it and try again. Thanks!
  • NotSoFastNotSoFast Posts: 3,059Member, Moderator El Moderator
    Over activation will have a ring of ink around it where it's pushed away from the hole like oil and water.
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