dtrs5kprs Posted February 26, 2005 Report Share Posted February 26, 2005 Not sure what happened to this post from Thursday night (removed???? or just lost). Anyway it is back with pics Basically a variation on the process of using an RTV mold and a smooth-on type resin to create a master, or mother mold. In the orifginal process resin was poured into an RTV mold to create a copy of themold, with raised features where the cavities would be. Then more RTV was poured in to the resin master (mold box) to quickly and accurately reproduce identical molds. With the rising use of aluminum molds the process requires an adjustment. For obvious (I hope) reasons, you cannot pour resin into your shiny new aluminum mold. This process overcomes the problem of the added step: 1) Place the aluminum original in the bottom of a heat resistant baking dish (corningware). Dish needs to be as samll as practical, and allow at least 1/2" additional depth over the aluminum mold. 2) Heat and pour enough soft plastic to fill the cavities in the mold, the areas outside the mold, and approximately 1/2" over the original mold. 3) When completely (important) cool, turn the dish over and place the plastic "block" on a table/counter/w'bench, with the alum mold's back showing. Carefully remove the mold from the soft plastic. Examine the raised areas that will form the cavities in the next step for quality reproduction of detail. If not ok, re-melt and re-do. 4) After the plastic has further cooled, mix and pour enough RTV mold compound to fill the "box" formed by removal of the alum mold. Concentrate on filling any ribs/claws/etc completely. As the RTV cures it will expand and slightly overrun the master box, so be careful of the surface you place the master on in this step (meaning...no cloth coverings). 5) When completely cured, remove the RTV. At this point you should have an exact copy of your original aluminum mold in RTV 6) To complete the process and create the resin master, coat the RTV mold and cavities with a mold release product and fill with one of the 2 part plastic resins (hard liquid plastic). When cured, remove the RTV mold and you should now have a hard plastic master that will allow you to reproduce the original mold in RTV over and over again. Big bonus of this is the $$$ saved, even with the RTV expense. Once you have your RTV copy (or an RTV copy) you can then trim around the outside of the cavities and edges to remove wasted space and reduce the volume of RTV required for each mold (like the Barlows molds). Given the $25-$45 price tag on some of these 2 cavity alum molds this is a big plus. The other big benefit is the reduction, or elimination of time spent setting up original baits for mold making (pinning or glueing down, mold box mfg, etc). Just mix the RTV and pour the mold. Will try to get the pics to post in the correct order, sorry if that does not happen. Also some apologies for the pics, shot them with my old camcorder...wife has the good digital camera for a weekend trip. If this post is going to be removed for any reason, please message me with an explanation. [Mod Note: restored] Quote Link to comment Share on other sites More sharing options...
GB GONE Posted February 28, 2005 Report Share Posted February 28, 2005 Dave....great tip!!! Have you tried this with resin yet??? Just curious as it should work just the same with a few slight modifications. Its just the technique I needed for some othe molds I have a limited amount of!!! Jim Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 1, 2005 Author Report Share Posted March 1, 2005 I have not tried to duplicate a mold in resin yet but it should work just fine. Only thing that concerns me would be the heat given off when it cures. Should note that the same concept used in the described process will work for any "hard" mold...meaning, while I used it to dupe an aluminum mold, you could also use the process to duplicate a resin/plaster/durham's mold. Just happened to have the aluminum mold handy when I worked on it, and the resin part sort of jumped out after the fact. Would have saved me a ton of wasted work back when I made lots of plaster molds, got a nice proto mold, then had trouble duplicating it. This should eliminate that issue. Quote Link to comment Share on other sites More sharing options...
Fish_N_Fool Posted March 1, 2005 Report Share Posted March 1, 2005 This works great for 1 sided molds I have used this same process to make molds before. However with 2 piece molds they don't ever seam to line up good enough to really work good. Although I have never tried it using RTV. Has any one ever made a good 2 sided RTV mold that lines up good and does not get a flashing? It would seam to me that they would bend to much and not stay flat together. Although you could back the RTV with some pegboard or plywood maybe. If anyone has a mold like that can we see some pictures of it. One thing you have to remember abour resin molds is they shrink {alot} I've had a mold 6" long shrink over a 1/2" so you would not end up with an exact copy of your original mold. Quote Link to comment Share on other sites More sharing options...
woodsac Posted March 1, 2005 Report Share Posted March 1, 2005 I have over 20 resin molds. I don't have 1 mold that has ever encountered more than 1/8" shrinkage. And 1/8" is the most. Most barely shrink at all. I would suggest trying less catalyst. The more catalyst you use, the hotter the mold gets while it cures. Therefore, the result would be more shrinkage. Quote Link to comment Share on other sites More sharing options...
vishezfish Posted March 1, 2005 Report Share Posted March 1, 2005 Cool concept!! You could probably use liquid mold rubber to make the first part ,,,, Master cast, then use whatever say plaster to make the actual mold from it!! I have to try it, I have some mold rubber too!! It might take a little longer to cure but I have it!! Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 2, 2005 Author Report Share Posted March 2, 2005 various answers to some of the above Q's: 1) You can make a nice 2 piece mold with RTV but it take a lot of work. I have one for an orginal wiggle wart body, that actually mold in the rattle chambers and all. Bugger all to pour it. Aluminum rocks for the full round molds. 2) Great additional tip on using the liquid mold rubber for the initial step vs soft plastic. That is the kind of thing I was hoping for by posting the info. Took me far too long working on my own to just figure out the steps as listed. Have only had time to make 2 mods from mine so far. Both look great and cast easily. Have not taken the next step of trimming and casting the hard master yet. Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 2, 2005 Author Report Share Posted March 2, 2005 Sorry for typing that last bit in Pidgin. Guess I either need to air dust the old keyboard or learn to type. Good thing compressed air is fun. Quote Link to comment Share on other sites More sharing options...
Mojo Posted March 2, 2005 Report Share Posted March 2, 2005 OK, what's the best (cheapest!) place to get quality liquid mold rubber? I found some that runs about $10 / lb shipped. A LOT cheaper than RTV at $19 / lb PLUS shipping. I assume you're using shore hardness a20, or do you prefer harder? RTV is really thick when you try to pour it at room temp, i.e. 70 degrees. I want something that will pour easily and leave a minimal amount of waste in the mixing container. If LMR is the ticket I can use it to make a master mold for the one-off stuff I design in sculpey. Pour some baits from the master and make a resin mold from them. I got exactly 2 master molds from the last lb of RTV I bought. Too much $$$ for my blood. Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 2, 2005 Author Report Share Posted March 2, 2005 Mojo, Unless you really work on minimizing wasted space (and thus volume) you will be doing well to get 2-3 molds per lb of RTV. By using the above process or the earlier mother mold process, you can trim the RTV mold before making the liquid plastic cast of it to reduce the volume. Basically, once you have the RTV copy, you can cut around the legs, claws, areas in between cavities, etc. Your mold won't be pretty and square edged, but you will still have RTV in the pot and $$$ in your wallet. Have not worked with the LMR. Suppose the effectiveness depends on what you try to make it do. Looking at your post...you could use the LMR for 2 things: 1) make the initial mold from your sculpey original, then use resin to cast a "reverse" mold in the LMR, and follow the above process to duplicate and produce your molds 2) if using a resin mold you already have, use the LMR in place of the soft plastic in the process above. I've been using the RTV for LC...10# kits. Have tried a few others, from non-lure sources with so-so results. Better to pay a bit more and be happy with the end result. Quote Link to comment Share on other sites More sharing options...
vishezfish Posted March 2, 2005 Report Share Posted March 2, 2005 I know of one website that sells it.. I ordered from monstermakers.com Or check out any special effects websites and they will have it for sale... They also sell rtv and silicone ... I started my mold in rubber today and it is coming out fine.. I have to recoat to get the thickness, it might take a little time... But again agreat great idea thanks for this cool post!! Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 6, 2005 Author Report Share Posted March 6, 2005 A follow-up...finding that the initial RTV mold will take a little longer to cure than an RTV mold poured in a "hard" box (wood, foil, glass). My guess is this due to the RTV being surrounded by soft plastic. They come out fine, just takes a few more hours than you would expect. Other option is to bump up the amount of hardener in the mix ratio. If I ever get done painting warts and rogues I might even get some poured Quote Link to comment Share on other sites More sharing options...
vishezfish Posted March 9, 2005 Report Share Posted March 9, 2005 The latex worked out fine but it took a little too long for me... So I got a new idea... I'm going to take some old plastics and melt them down and pour them in my master mold ... Let it over flow to capture the whole mold so I have a master cast... I will repeat that as much as I want to make more molds of the casts... It seems to be faster cuz the plastic will cool quicker then the latex...... Hope this helps anyone who might want to try it!! Quote Link to comment Share on other sites More sharing options...
nova Posted March 9, 2005 Report Share Posted March 9, 2005 VF that's exactly what I do and it works great. Just be careful of bubbles. Before you pour the plastic let it set for a minute so the bubbles will rise and you can deal with them. After the plastic cools I pour resin in the master and in a 1/2 hour you have a working mold. Quote Link to comment Share on other sites More sharing options...
vishezfish Posted March 9, 2005 Report Share Posted March 9, 2005 Cool deal Nova! I'll look out for the bubbles thanks for the tip!! Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 9, 2005 Author Report Share Posted March 9, 2005 Curious...doesn't this method slightly increase the size of your bait vs the proto? Quote Link to comment Share on other sites More sharing options...
GB GONE Posted March 9, 2005 Report Share Posted March 9, 2005 OK...you guys have confused me a little here...(Which is NOT hard lately!!!) After you pour plastic over your aluminum mold and remove it, you are pouring plastic back over the plastic (instead of RTV)???!!!! Then casting that plastic with resin!!!! I must have plastisol on the brain (I've blown through 3 gallons of plastic in less than 2 weeks) or something cause I'm not getting it!!! Please enlighten me again as I get Dave's way!!! Jim Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 9, 2005 Author Report Share Posted March 9, 2005 As I understood that post...they are pouring soft plastic over the proto bait, then resin. Not sure how this would work, see some problems, but I certainly could be off course. If you could somehow resin coat/hard liquid plastic coat the proto you might be in business. Quote Link to comment Share on other sites More sharing options...
nova Posted March 9, 2005 Report Share Posted March 9, 2005 The baits I posted in the photo gallery are made with this process. First the plaster mold then the plastic master then the resin. Quote Link to comment Share on other sites More sharing options...
vishezfish Posted March 9, 2005 Report Share Posted March 9, 2005 Nova hit it right on the nose... U pour some old plastic in a one part mold...(yes u can use my worms i sent all of u!!) Overflow it so it goes all over the top of the whole mold.... Let it harden,,... Then u take it out... There is your cast...!! It should be the bait attached to the bottom now... Now, I use plaster, ( i'm not professional yet!!) Pour your plaster over the cast and u have your mold ! Just like u do when you make a mold of your clay prototypes... same thing only now you can make say ten molds that will be exact ... and then u can put them together... if you make ten pours and make the ten molds.. U should get a exact mold each time... Hope that clears it up!! Quote Link to comment Share on other sites More sharing options...
dtrs5kprs Posted March 10, 2005 Author Report Share Posted March 10, 2005 Got it. Basically talking about doing the same thing I think, just different mold materials. Quote Link to comment Share on other sites More sharing options...
vishezfish Posted March 10, 2005 Report Share Posted March 10, 2005 Yes sir, thats it!! Good luck! Vf Quote Link to comment Share on other sites More sharing options...
