Casting Paper First try

Discussion in 'Tips, Tutorials & Tools' started by Sticky Fingers, Feb 9, 2004.

  1. We all remember the thread from the old site that Gil had running about just how far one can "stretch" paper. I have been thinking about this foe a while and finally decided to give it a try. But first I read up on the subject in a handy volume titled "The Prop Builder's Molding and Casting Handbook" by Thurston James. Covers all kinds of quick and dirty along with easy casting methods and products that can be used for producing molds. I'm sure that the library systems in larger cities and most colleges that have any kind of theatricasl department would have this. Copyright 1989 and listed for $19.95. ISBN #1-55870-128-1

    Got my first molds curing right now. Gonna try making copies of the BMW 14 cylinder radial to use in Roman's FW-190 F-8 from Digital Navy. I'm using Plaster of Paris for the molds as there are no undercuts and "She who must be obeyed" really objects to the smell of RTV silicone. Will post pictures of the mold and parts soon (fingers crossed :? :? :? :? :? )

    PS Is the old site dead? I haven't been able to access it since about saturday morning.
  2. Ron

    Ron Member

    Mark, I'm looking forward to that one! Maybe a cowling for that model too? Thats the only thing preventing me from grabbing it.

    The old site is not gone but stuck out in etherland. When they send me the url, we'll have access to it again for about 5 months

    All the best

  3. rickstef

    rickstef Guest

    for the time being yes, plus Ron and I have been talking about converting the posts that are there to a text file and use it as an archive. but more will follow on that one

  4. I really would to love to see the archieve if possible. I wanted to print up a couple of the tutorials ( Stretching Paper and the Recolouring one). If any one has them could they send me a copy in my email. That is if Ron, Gil and the Swedish gentleman (his name escapes me right now) don't mind
  5. rickstef

    rickstef Guest


    Check the Articles button at the top, you should be able to find some of the stuff you were asking about

  6. Just pulled the mold from its former (sherbet container cover). First lesson. Plaster has a pretty high specfic gravity. so if you use something like the described former for the mold make sure it is supported in the center not the outside edges. Other wise plaster can flow under the parts. No big deal to clean up the parting lines as long as you pull the mold before it cures completely. The excess scrapes right off with an excato blade pulled backwards. Now the trick will be to see if patterns courtesey of Hasegawa will pop up tommorow.
  7. Ron

    Ron Member

    Mark, Just did your casting turn out?

    I managed to download the entire old site. After a long period of arguing with tech support about a temporary url, I gave up and settled for just getting the files and databases. Rest assured our information is safe
    and backed up. Since that entire site was almost completely stored in a database, there is really no way to retrieve it as it sits. I think the solution is to find some free hosting somewhere but that might be an issue as we would need about 200 megabytes of space on NT hosting. I desparately want to make this available for us

    I'm rambling again ......

  8. The first try was an unmitigated disaster. The product I was using, Celluclay, was pretty uncoprative as far as being forced into the molds. While it did pick up some detail such as cylinder cooling fins and pushrods it mostly came out as a featureless blob of cellulose. I think the problem may be with the molds somewhat too. When I poured the plaster it may of been too thick and not picked up details like I would of liked. I did find a Woodland Scenics Latex mold making material at a local MRR shop (list price about $12US for 1qt/) and am going to give that a try too. one thing with the plaster molds is I think that you have to have a piece of dowel or something sticking up through the plaster so as to provide a place to push the casting from the mold instead of having to pry it out. A lot less chance of really screwing the casting up. Trying to avoid these pit or pratfalls is one reason I was asking about the Stretching Paper thread. Maybe Gil in his enormous :roll: spare time could write up a tutorial. I'd be willing to do one too if I can get a good handle on this

    PS One word of caution. Latex for mold making has an ammonia based solvent in solution that acts as a catalyst when exposed to air. This stuff smells nasty. While the material is not really recommended for paper mache i'm still willing to give it a go. If it doesn't work there's always plaster. It may not be paper but at least its not plastic. :wink:

    PPS has anyone out there used the Silicon rubber mold making process. Micro Mark has it but I'm a little leary about simply based on their word. I'll probably try the RTV Dow Corning Silcone too but that stuff smells up the house to much and it is too darn cold to do it out in the garage. :(
  9. Ron, if you have to just bite the bullet and maybe put it on one that sells advertising. I think we could put up with some pop-ups if we had too
  10. I spent two years working with resin casting. Eventually I'll get around to painting the Kyutei Honis, Mecha Gojis, and Guyver1s...
    My supply house was mailorder down the coast from Douglas & Sturgess:

    Straight latex mold is probably too elastic for pressure molding (injection, expanding foam, press laminated films, pressed in clay, paper), backing it with plaster for support may work.
    I have not yet experienced RTV with a potent odor while using tin catalyzed "blue" type.
    You may want to check polyurethane rubber (D&S had an isocyanate-free type) and vinyl rubber (may be too hot though) as additional possibilities.
  11. wunwinglow

    wunwinglow Active Member

    Casting resin, RTV moulds etc.

    I cast in RTV for my living!

    Silicone rubber, condensation cure ( blue/white, smells of vinegar) is the usual stuff found in hobby stores. We don't use it, the catalyst poisons our other materials. However, catalyst quantity is variable, to a point, and not critical. Rubber will leave a deposit on the master AND your castings which will prevent water-based paints adhering. This is difficult to remove, especially if you want to paint the moulding. Most solvents, soap, detergents etc won't touch it, it needs to be abraded; gentle sand blasting is good.

    Silicone rubber, addition cure. Various colours, although the stuff we use is clear. Almost. Mix is fairly critical, and cure is done at 40C.

    Polyurethane resins. We use Polyurethanes to cast in the RTV moulds, ie the part, not the mould, but no reason why you could not make a mould with them. Hardness' vary from extremely floppy (20shoreA) to so rigid and tough you can stand on them. A mould made of this stuff would last forever!

    All our castings are done with reacting chemicals, under a pretty good vacuum, and cured at controlled temperatures for dimensional stability. The various 'hand' casting materials might be better and easier to handle if you don't have access to a vacuum chamber.

    One common problem with all of these materials for casting a 'wet' material like clay is that the resins are all impervious to water, so the moulding will dry out from the back. The surface against the mould, where all the detail is, will be the last bit to dry. Using a plaster of paris mould which is porous, the mould will draw moisture out of the moulding, and the moulding will dry more evenly. With a material like papier mache which has a glue binder, having that soak into the mould probablly will bond the mould and casting together! Eek!

    Making a copy mould with silicones is easy, they don't bond unless the pattern is porous. PUs will probably stick like the Devil unless you use a wax release agent (aerosol). I will look out some tutorial websites on moulding and casting, which will apply to this problem.

  12. neoneanderthal

    neoneanderthal New Member

    has any one tried drop forging paper sheets ... just curious ... :)
  13. Gil

    Gil Active Member


    Using the latex to extract detail from a mold is probably your best method. You will need to paint or dip the latex on the model to build enough thickness to stabilize it once removed from the master. You will then need to backup the latex with plaster to insure that things remain stable. The 100% cotton paper slurry can be then be press mopped into the mold to an adequate thickness and left to dry. Use beeswax dissolved in turpentine as a mold release agent (yes beeswax is dissolved by turpentine). The paper will shrink away from the mold as it dries and might cause a problem of sticking due to "pinching curves". The addition of methyl cellulose to the paper slurry does a good job of stabilizing the fibre shrinkage and adds a degree of strength to the final result. The dried paper mold can then be carefully picked out of the mold and prepared for finishing.

    Best regards, Gil

    P.S. The stage craft book details how to best mix plaster by sifting it into the water...., this is the best method for mixing plaster. A bit tediuos but the results are more than worth the effort.
  14. Decided to bite the bullet and buy some Silicon RTV from a hobby supply house. The cure time on Latex and Silicon sealant is a downer. That was last week. Got by the ups man yesterday just in time for my birthday. So as not to get she who must be obeyed mad decided to do the first test molds at work. Used 1-1/2" PVC pipe for the mold formers. Detail tranfer to the mold was quit good. and the patterns popped right out no problem. I do have some clean up of the parting lines to do from silicon creeping under the pattern. Plus I forgot to allow for the index pin on one of the parts (1/32nd BMW radial from a Hasegawa kit) so that left a little more seepage on one of the molds. The PVC worked great. While I have access to a full machine shop this stuff can also be cut very nicely on a table or chop saw if one is available. Will post pictures soon

    Ron, could we move this to Tips and Techniques?
  15. RyanShort1

    RyanShort1 Member

    After having worked for a beekeeper about 8 months last year, I can definately second this. When we use the "hive tools" and they get all junky with wax, we use turpentine or thinner to clean them up.

  16. Actually with silicon you really should not need any release agent. I just did a couple of tests with Plaster of Paris. I had the plaster a little on the thin side just to make sure it flowed alright. Filled themolds beautifully but a thin mix will leave the Plaster a little on the weakside. Next up is to try one with Durhams Rockhard Water Putty. As I am mainly trying this for detail parts and such it doesn't really bother me to much if I can never get paper to work out but that's the next test after the Water Putty. And I would post some pictures but I am having camera problems in that the files are to big for the site even at lowest resolution :x

    ARMORMAN Guest

    I have spent several years dealing with resins and rubber molds.

    I would recommend dealing with this guy:

    TSB Plastics

    He doesn't do a large markup and ships practically everywhere. He carries several corporate brands, but primarily deals with Smooth-On products.

    He has RTVs that can cure under 2 hours (for those who are very impatient)

    Also, there is a product made by a company called Aves Studio ( for making push molds, but I can't recall the name (I usually just buy their ApoxieSculpt product for making masters).

    My two cents.


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