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Bondo/resin mold casting Question

Discussion in 'Molding and Casting' started by John, Jan 22, 2009.

  1. John

    John Member

    149
    0
    Iowa
    I made a fish mold out of Bondo/resin and then. I used Carnauba wax and coated the inside of the fish mold and then. I used the WASCO's gelcoat and then coated the fish mold with fiber glass resin.and clamped the mold together let it set for about 4hrs and then .I went to pull the mold apart and you got it. I ened up having to toss the mold in the trash. Both parts of the fish mold were stucked together and. I even Broke the mold trying to pry it apart .what would have caused the mold to tick together. like that

    I have other fish molds that are made of Bondo /fiber glass and I dont want the same to Happen to them so until I figure it out I am at a stopping point

    any input would be great
    thanks
    John
    I am thinking that I added to Much gelcoat not sure
     
  2. Kerby Ross

    Kerby Ross KSU - Class of '83; U.S. Army - Infantry (83-92)

    Maybe

    I do 2 coats of car wax (Mothers Carnauba Cleaner Wax) on the fish part, buff. Then I use Vaseline Jelly on the non-fish-part (Gel Coat won't stick to Vaseline Jelly). I also use the Vaseline on the edges. It won't stick that way. The only difficulty might be undercuts as the bondo is stiff and there is no flexibility in a rigid mold. Soaking in hot water when prying apart with a screwdriver helps.

    Kerby...
     

  3. John

    John Member

    149
    0
    Iowa
    thanks for the tip .I have always used Vaseline and thought. I would try the mothers carnauba cleaners Wax with no Luck. I think I will play with the car wax some more but not on any of my good fish molds. I will also try the hot water.
    again thanks for the tip.
    John
     
  4. John

    John Member

    149
    0
    Iowa
    Just an upday on my post. since this post. I thought. I would Just try the Vaseline and not the Car wax Carnauba.
    I am making a 17 1/2" Rainbow trout repo this is 1 of my own Molds after. I put the Vaseline on the mold side were. I will be putting the Fiber Glasss resin.and then. I used the gelcoat from WASCO's let it set up and then .I put the fiber glass resin on the mold side that .I will be casting and know. I can feel the resin kicking got hot so know .I know that the resin is getting hard and. I will be able to pull the mold apart and should have a good casting of the rainbow trout. I will post a photo of it once. I pull the mold apart.if it turns out LOL.
    John
     
  5. Kerby Ross

    Kerby Ross KSU - Class of '83; U.S. Army - Infantry (83-92)

    John,

    I only use car wax on the fish mold.

    I use the petroleum jelly on the flange or edges, not on the fish mold part itself. Gel coat doesn't stick to petroleum jelly so that would defeat the purpose.

    Plus I use Gel Coat first, then followed by fiberglass resin mixed with Cab-o-Sil and fiberglass cloth, then Gel Coat on the seams just before clamping the 2 halves together.

    [​IMG]

    Kerby...
     
  6. John

    John Member

    149
    0
    Iowa
    kerby Hi .
    if. I can get this photo to up load .I will post it to show the out come. I dont have any Luck using the wax so .I am sticking with the
    petroleum Jelly. were the gelcoat doesnt stick the resin does the fish repo looks like it has tons of holes LOL but it really doesnt .the fiber glass resin fills up were the gelcoat doesnt once the fish repo is cleaned up and primed you wont even see the resin spots

    but. I think. I am going to try the car wax again. but on a old mold so .I dont risk losing a good mold .I will try to upload the trout repo .

    John
     
  7. GBRUCH

    GBRUCH "I am nothing without christ".....John 15:5

    apply 2 light coats of wax and then apply 2 light coats of pva.

    soak the whole shabang in hot (near boiling) water and you shoud have good luck.
     
  8. Did you seal the mold? I always seal the mold with shellac by cutting the shellac 50/50 with denatured alcohol, it may take three or four coats.

    allow to dry between each coat, then wax and buff, wax and buff wax and buff. allowing the wax to dry to a haze between each waxing.

    The replica should pop right out. if not you dod not have the mold sealed and waxed.

    I have some bondo resin molds I have pulled 30 fish out of and they have not even started to breakdown.
     
  9. fishdude

    fishdude New Member

    169
    0
    Wax and buff twice then use two coats of PVA sprayed thru an airbrush with a #5 tip. Allow each coat to dry thoroughly. Spray the entire mold, detail and flange. Forget about the vaseline on the flange, it's not needed if you use pva.. One note, before the first waxing I use apoxie sculpt and blend over any rough areas such as fin bases for the paired fins etc. Using this method the two halves don't just fall apart. You'll have to use screwdrivers and work your way around the entire mold to pull off the first half. To remove the fish from the bottom half I use a piece of 1/4" plywood such as floor underlayment cut 3/4" wide by a foot long. I taper one end so it's wedge shaped. I start it under the tail and tap it with a hammer to drive it down the side of the fish. The wood is soft enough that it does not damage the mold. Before it reaches the base of the anal or dorsal fin the fish should pop out of the mold. I have demolded 6 fish in the last two days using the above method with no problems. Good luck
     
  10. I use a mold release system from composite one treat your mold using the directions on the cans.I have pulled a thousand pieces out of a mold without treating it again.
     
  11. Speckled Trout

    Speckled Trout Member

    549
    1
    Can you explain this a little more?
     
  12. Mold release systems are usually a 2 part treatment for FRP molds. Although expensive about 200.00 for a gallon of each.I have been building molds and casting for along time.When I treat a fish mold it's treated, spray gel coat then let it tack to touch and chop it.When the plug is pulled it's down right spooky at first the way it comes out.Don't gel coat and leave it for later on because the gel coat will prerelease [not pretty] I have pulled 8-9 pieces a day out of one mold that weighed 30#'s a piece that's rockin and wouldn't treat but every six months and pieces would actually release themselves most of the time.One thing to consider is small under cuts or irregularity's in the mold itself either fix them or learn how to deal with them. But Im over the paste wax thing use very little now used to use 3-4 cans a day down to a can every three months just for wiping tools.