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Casting - molding question?

Discussion in 'Fish Taxidermy' started by LionHeart, Mar 6, 2010.

  1. LionHeart

    LionHeart New Member

    Hi guys, I have a couple of questions about casting-molding procedure.

    - Can I use fiberglass resin instead of polyester resin when doing a bondo/resin mold?

    - I've made a mold, then a cast of the fish and like how it turned out. Now, to make a "production mold" do I use the cast as if it was a whole fish or use the original mold? ??? or... :-\ May sound noob but I am a bit confused here lolll

    - Also, how many copies could one expect to pull out of a bondo/resin mold?

    Thanks
     
  2. Pescado

    Pescado Biggest in 2011

    - Can I use fiberglass resin instead of polyester resin when doing a bondo/resin mold?

    I am fairly sure they are the same.

    - I've made a mold, then a cast of the fish and like how it turned out. Now, to make a "production mold" do I use the cast as if it was a whole fish or use the original mold? or... May sound noob but I am a bit confused here lolll


    Production molds are usually done with a cast from the original which has been touched up or chased as some put it.


    - Also, how many copies could one expect to pull out of a bondo/resin mold?

    I do not use bondo for molds. I can say that silicone, especially platinum, will give you the ability to cast many fish, as long as you do not have severe undercuts.

    PB
     

  3. GBRUCH

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

    I will add tp Pauls post.

    You can get 1 - 7 (that is the most I have gotten from 1 mold) but the best detail will be on the first one. Any severe undercuts will break away in the mold after the first pull.
     
  4. LionHeart

    LionHeart New Member

    Paul, thanks for the reply. ;)

    When you guys mention "undercuts" what exactly does that term mean? ???


    Gary, are you referring to bondo mold or silicone ones?
     
  5. Mike B.

    Mike B. New Member

    488
    0
    "Undercuts" are your detail area's like around the maxillary bones in the head. These little detail sections tend to break off before they pull free.

    Gary is talking about bondo molds I believe.
     
  6. It is a matter of how your masters are constructed.
    If you resolve some undercuts and are creating a flexible thin yet reinforced mold out of fiberglass you will be able to get more.
    I have a few fiberglass molds that are going on 30 pulls and still going strong.
    It really depends on the species and mold.

    I would recommended silicone for master molds though, although many of my masters for larger fish are fiberglass.
     
  7. LionHeart

    LionHeart New Member

    Ah ah, got it Mike, thanks for clarifying, I appreciate :) I am french so some terms/words I don't use often are sometimes unclear ::).

    Josh, it's a 24in walleye, I was thinking using a brush on liquid rubber mold builder then make a reinforced shell around it to "sit" the rubber mold in. So when time to pull, it would be very flexible as I would only have the rubber to work with.

    Something like this that I can find locally, unless there is something better you can see on their site
    https://www.wallacks.com/catalogue/catalog.php?cat=pm7&table=ceramics
     
  8. The latex may work, but it will shrink and over time your mothermold will not line up with the rubber.
    If you have to go locally I would look into using Silicone caulk with a dab of paint mixed in to kick the reaction.
    It will take you about 4 - 6 tubes for a walleye that size.

    Its not Ideal and RTV silicone would work much much better.

    Most of my walleye molds are fiberglass and the head is molded in silicone.
    I make my molds thin with several layers of fiberglass matting for strength. They are holding up fine after a dozen casts each.
    I do save my original as a master if I need to make more molds.

    I have not had the best luck with latex, but perhaps others have.
     
  9. GBRUCH

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

    Yes, I was speaking of Bondo molds.

    Bondo/ Resin molds the way I make them are not designed for many pulls--I only care to get one and from there can remold if desired.


    I agree with Josh an RTV would be my choice over latex.
     
  10. Cory

    Cory Keep an eye on quality!

    SO.......................am I understanding that some molds are done with, lets say, RTV and then hardshelled over the top to allow the clamping together of the two halves. Would bondo work over the top for the hardshell? Jknuth, how are you molding the head in silicone and the the body with fiberglass. Are you molding the whole fish and then removing the head and molding the head in silicone? And when you save the master, would this be the first pull from the mold?
     
  11. LionHeart

    LionHeart New Member

    Many thanks man, I had not thought about shrinkage at all, glad you mentioned it. I have to go there sometimes next week, they might have something like RTV silicone instore that's not on their website.

    Gary,

    Thanks for your input, you guys are the best ;D
     
  12. I would not use straight bondo. I would use reinforced fiberglass resin with fiberglass matting.

    As for molding the head, there is about a thousand ways to do it.
    normally I mold the head on the fish then cut the head off and mold the body with the first set of gills attached to the pectoral collar.
    You could also mold the fish then remove the head from your first casting and mold it separately.

    how ever you do decide to do it just make sure to get the head to sit naturally on the body when all is said and done.
     
  13. LionHeart,
    This is my 2 cents worth...
    For Warm water fish, that are say 24" and under, I would mold with a flexible material, RTV, Urethane etc. of your choice. A walleye has fairly durable skin and should mold well. You could mold with plaster or bondo/resin, chase and mold the master, but...I don't think you would need to.
    I have also found that each time you mold the "master", you run the risk of losing scale detail. Your best detail will be directly from the fish, 1st molding.
    Also, multiple pulls from a mold like this will be a breeze...
    I just hate to work, smell, grind,demold or breath fiberglass. Once again, good results can be achieved in different ways..Good Luck !

    fyi....I'm headed out of town, (for a week), this morning and will be unavailable for any "follow up" ques. that usually are generated, from molding / casting threads.
     

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