13 replies to this topic
Posted 13 December 2009 - 06:19 PM
A friend came up to me today and we were talking about fishing and molding came up and he told me that it is possible to mold an object with plaster of paris and seal it to make a mold. i was just wondering if anybody has tried this yet?
Posted 13 December 2009 - 07:25 PM
I tried the plaster of paris (Plaster of Paris) thing once. I didn't have much luck and the results weren't what I wanted. I have heard of several people doing it though... especially with soft plastics. Most people use RTV silicon to make 1 or 2 piece molds.
Posted 13 December 2009 - 09:49 PM
Plaster of Paris (Plaster of Paris) is an excellent molding material. It is not the best choice for casting hard bodies though. A general rule of thumb is 'hard cast - soft mold'.
RTV would be a better choice for hard bodies. Also, check out Husky's thread on water cured silicon RTV:
Posted 14 December 2009 - 01:03 AM
I do not think it will work for hard baits unless you are makign half round objects and gluing them together. I have been making soft plastics in Plaster of Paris for years. I have cast lead in it too and only if you do not have an under cut can you get it out. I tried some casting resins and epoxy with them and the results were not good, the stuff always seem to stick no matter what I used. I never tried lures but was trying to repair things with cast parts.
Recently I saw a video on one of the RTV suppliers site on making repair parts. By far from what I saw the soft material is the way to go. They used a system where the edges of the master were outlined with tape and they cast it into a block of clear RTV and then cut out on the tape line to make the two halves. A bit different than making two piece for soft materials.
Edited by Piscivorous Pike, 14 December 2009 - 01:12 AM.
Posted 14 December 2009 - 04:51 PM
Hey Thank You Guys soooo!!! much i will definitely be molding soft plastic in Plaster of Paris then seeing as how it is way cheaper. Would pouring lead also work?
Posted 14 December 2009 - 04:58 PM
I made giant bullet sinker with a center pin in lead.
Just remember that Plaster of Paris decomposes from a set product back to plaster when heated over 150 F. You can only get few lead casts from a Plaster of Paris mold before they are shot.
Recently I made a new Plaster of Paris mold and was drying it in the oven, I can only get it down to 170 so I watch it close when the moisure is out it is done.
This time the preheat was left on at 350 for 2 hours. The new mold was crumbly and you could pinch it to pieces, back to plaster. Good demonstration but it was back to the starting over.
Posted 14 December 2009 - 09:54 PM
I tried this recently and it has worked reasonably well me so far, although I have only molded a few. I was looking for the most inexpensive way to mold my own soft plastics and that is what I came up with. I bought some Plaster of Paris from wally world. Built a cardboard box about 12 x 6 inches using strips of cardboard taped together with duck tape. Lined the inside with aluminum foil, greased the worm I was using as a model with a thin coat of vaseline, placed it in the bottom of the box with the flat side of the worm facing down (cant make completely round worms this way). The vaseline helps hold it in place while the plaster is being poured over it. Mix the Plaster of Paris, pour it into the box enough to cover the model worm about an inch deep. When the plaster is set turn the box upside down, remove the foil and model worm from the plaster. Go back to Wally world or if you're smarter than me just pick up a can of heat resistant car engine paint at the same time you buy your Plaster of Paris. Paint the mold and let it dry completely. The paint helps keep the plastic from sticking when it dries in the mold. You can also use a small amount of vegetable oil in the mold if you desire. I have a ton of old plastics that were battle scarred and too beaten up to use again but I never throw them in the water for fear a fish my swallow them and die so what I do is melt them down in a gravy pan or any pan with a spout over no higher than medium heat. When the plastic is liquid I pour it in the mold, let it cool, remove it, cool it in a pan of cool water, and trim it up with a utility razor blade. Like I said this is a very elementary way of doing it but it is also the cheapest way if all you want is a few worms at a time and you are just looking for something to do with all your old scrap plastic. One tip is dont try to mix colors always melt the same color plastics together. If you want multi colored worms melt the colors in seperate pans. You can also make custom molds this way by using different parts from seperate worms as your model. I made a worm with a craw claw at the tail and three tenacles coming out each side. I caught a three pound spot on it a couple weeks ago so I know it works.
Posted 21 December 2009 - 04:24 PM
Hey wow thanks guys that is great congrats on the Three Pounder. Last night i tried doing the silicone thing that vodkaman posted with the link to husky's post that is extensive knowledge on the subject but yeah my silicone still hasn't dried yet and i don't think it will turn out that well probably cause i used the wrong the silicone but i am gonna go get some Plaster of Paris and try doing the same worm as the silicone mold that i did last night and see how it works wish me luck!!
Posted 23 December 2009 - 01:07 AM
hey what do ya know Plaster of Paris works great for worms thanks guys so much. will post pics of how i did it in soft plastics pretty much did what Lance did with a few deviations worked very well although the plaster doesn't really need to be an inch thick oh well doesn't matter but thanks for the help i wouldn't have plastic worms without you guys it really helped
Posted 23 December 2009 - 03:22 AM
Don't skimp on the plaster, it is very cheap. Sooner or later you will regret it and the mold will crack in the middle of a pouring session. The 'inch thick' advice appears many times through the posts on TU and is given from experience.
Keep up the good work and I look forward to your pics and explanation. Even if a lot of the method is duplicated, it is all good reference material.
Posted 27 February 2010 - 10:44 AM
Have you guys experimented with other nonstandard mold making materials for plastics?
I've been reading the various threads and coments about plaster of paris molds for a couple months and I have been wondering about other materials. Obviously one of the best materials is CNC cut aluminum. I have a hobby level cnc machine and I can cut aluminum, but the time to do run is very long due to the small amounts of materials you can remove per pass with a tiny cutter.
What about wood? Or bondo? Or chopped glass filled fiberglass? Or Wood's metal (or one of the related alloys)?
I realize a lot of bait/mold makers do not have access to a cnc machine of any class, but is Plaster of Paris the only mold material that seems to work out well for the home or limited budget bait makers?
Primarily I am referring to molds for softbaits in this case.
Posted 27 February 2010 - 10:52 AM
I will answer, since it just popped in and I am logged in.
Plaster of Paris, plaster of paris
DWP, Durham Water Putty
RTV, Room Temperature Vucanized silicone rubber
All work well for limited commercial production and hobby. All of these have various qualities, but for the most part can be used for open one piece molds or two piece molds. RTV has an additional feature of being able to be made into a clam shell semi full enclosed mold.
RTV has many varients of hardness and mix ratios, colors and costs.
Water putty gets rock hard, which is also a trade name of the substance. Plaster of Paris is the cheapest and least durable.
Plaster of Paris and water putty need to be sealed after making.
There are tons more, please use the search feature, this post is full of key words to work with.
Posted 27 February 2010 - 10:59 PM
RTV silicone is preferable IMO to Plaster of Paris. Making Plaster of Paris molds is good practice since RTV silicone isn't as wonderfully inexpensive as Plaster of Paris, but still affordable.
Silicone molds are durable, flexible, and easy to do-it-yourself.
I don't know much about CNC machines, but THEORETICALLY if you used one to carve out your mold from a block of wood, you could seal it with a very thin coat of epoxy (not too much or you start to loose details such as scales and carved gillplates or anything similar) and pour yourself some soft plastics probably.
Edited by mainbutter, 27 February 2010 - 11:01 PM.
Posted 02 March 2010 - 11:11 PM
just an update on how far i have come on this subject. this last weekend i took and made a two piece mold of a real crawdad from plaster of paris very difficult but doable
impossible is not a word it is just a reason for someone not to try.