borderbasser Posted December 24, 2008 Report Share Posted December 24, 2008 Hey guys. It has been awile since I have posted over here. I have been hanging out over yonder with the hard bait croud for a while:eek: Anyway, I have a swimbait that I want to make some mods to, and then mold it in a two piece mold. I would prefer to do it in RTV since it doesn't have to be sealed, but am open to using plaster. I am not a stranger to making two piece molds, but I always seem to have a problem when it comes to pushing the bait half-way in for the first half and getting it exactly right. It always seems that the plaster is too thin and it sinks, or the plaster is too firm and the edges of the plaster around the bait pull in (if that makes any sense). I have seen in the hardbaits forum before the crash, where some where using a clay bed to push the bait into and then build up and smooth the clay up to the center line of the bait to pour the mold material on for the first half. Then, turning it over and removing the clay so that the second half can be poured. This seems pretty labor intensive and while feasable on a hard bait, it seems like it would be a little more difficult with a soft bait although I have never tried it with either. Do you guys have any tips for achieving a good perfect centerline for your baits? Any tips concering this with RTV molds would be most helpful, but tips for plaster would be more than welcome too. Thanks guys. TJ Quote Link to comment Share on other sites More sharing options...
Delw Posted December 24, 2008 Report Share Posted December 24, 2008 (edited) Making a swimbait mold out of RTV /pop you can pretty much make it a one piece mold( if you have a open top) as RTV bends and will pull out a finished bait nicely with out ripping a fin or 2 off. plus with that amount of plastic there is alot of elasticity. I would make the swimbaits out of one piece of alum. if it was do able. as a machine can only do certain things with certain tools. it gets really costly when adding 4th and 5th axis attachments and very long small dia tools to do the job. For example that Chub "E" mold I have I can make out of one piece however it would end up costing about 3k per mold, on a production level an easy 700-1000 bucks per mold ( just a guess but its a close guess) to make a 2 piece as close to center line as possible I would get a piece of sheet metal like .040-050 thick. cut 2 holes in it opposite to hold someone round like marbles so the mold will seat together. cut out a space for the sample to fit in also. then pour the RTV/POP in it complete, let it sure and take off the sheet metal( with the 2 marbles attached) you will only loose .040-.050 thickness of the bait. then pop a marble back in each socket and glue it in place, you then have a 2 piece mold with flat and even faces that ling up correctly using the marbles. Edited December 24, 2008 by Delw Quote Link to comment Share on other sites More sharing options...
borderbasser Posted December 24, 2008 Author Report Share Posted December 24, 2008 That is a good idea and it reminds me. One of the hard bait guys next door uses a block of wood and cuts out the profile of the bait in the center of the block. Then, he puts the bait in with the centerline even with the top of the block and then uses putty to seal the gap between the bait and block. I'm sure your method would have to incorporate a small amount of putty as well to seal the gap which really is not a big deal. The fins would probably have to be only in one side of the mold, but that wouldn't be any big deal i don't guess. Thanks for refreshing my memory Delw. TJ Quote Link to comment Share on other sites More sharing options...
HJS Posted December 26, 2008 Report Share Posted December 26, 2008 TJ - I've made several 2-piece molds out of Dunhams Water Putty... just like PoP but better in my opinion. Sets up a little slower and seems to get harder. And you are right, placing the masters in the first layer is indeed tricky and is crucial to the success of the mold. When making my last several molds I pushed a round toothpick (actually, 1/2 a toothpick) into the mid-section of each master to make handling a LOT easier (see pic). Helped out a lot!!! BTW, I remove the handling toothpicks before pouring the top layer. And yeah, the thickness of the PoP batter is also all-important for the reasons you listed. You want to avoid at all costs having the PoP pull down, or pull up, along the sides of the lure because that results in a sharp edge of PoP that will flake off easily after it get hard... edge flaking is a major PITA. The toothpick helps in getting the lure situated at the right depth. Sometime, when my batter is too thin and my lure sinks too far into it, I'll take it back out by the toothpick, wash off the master, and wait an additional couple of minutes until the PoP or DWP gets a shade harder. BTW - the stubby little piece of toothpick shoved in the nose of the master lure is there to mark the center so I can drill out a pour hole and a bigger reservoir hole. There seems to be no accurate recipe for mixing PoP or DWP so its just right. Just a splash too much or too little water and the mix is not exactly right. 5% vinegar in the DWP slows down the working time at least 15 minutes... plenty of time to get the masters in right. But regardless of my best efforts, after the first layer is hard, I'll notice a few spots where the PoP has pulled up on the side of the lure just enough to be annoying. I'll wait for the 1st layer of PoP to harden completely, then, with the masters still firmly in place, I use a very tiny "paint scraper" I made out of a flattened, sharpened & bent nail and scrape away the raised edge until its flat with the rest of the mold. Only takes a couple of minutes to touch it up. I do this with all the finesse of a doctor doing microsurgery. On the other hand, dunno what you can do if the PoP has pulled down. For me, that almost seems impossible to correct without compromising the quality of the mold. I know on 2 separate occasions I dumped out the "too firm" PoP and started over trying to mix the PoP a little thinner. Good luck. Quote Link to comment Share on other sites More sharing options...
jimcline Posted December 27, 2008 Report Share Posted December 27, 2008 Just curious about what everyone uses as a mold box. The only thing I've been able to find is pie tins but I really don't like the shape. I've really got to try the water putty, POP is a royal pain. Appreciate any help, JIM Quote Link to comment Share on other sites More sharing options...
Richard Prager Posted December 27, 2008 Report Share Posted December 27, 2008 Just curious about what everyone uses as a mold box. The only thing I've been able to find is pie tins but I really don't like the shape. I've really got to try the water putty, POP is a royal pain. Appreciate any help, JIM It's the thread below this one. http://www.tackleunderground.com/forum/soft-plastics/15467-quick-easy-mold-box.html Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 27, 2008 Report Share Posted December 27, 2008 POP is a royal pain. Jim, I don't understand. For me, PoP is the easiest medium to work with. Maybe you should give us a run down of your method and what the problem is. You are going to have the same problems with DWP. Dave Quote Link to comment Share on other sites More sharing options...
jimcline Posted December 28, 2008 Report Share Posted December 28, 2008 Jim, I don't understand. For me, PoP is the easiest medium to work with. Maybe you should give us a run down of your method and what the problem is.You are going to have the same problems with DWP. Dave Dave, most of the problem I'm having with POP is consistency. I swear it doesn't matter how many times I mix according to instructions it comes out a different consistency. So of course I'm getting different set times. Also, it tends to flake a lot and turn up on the edges of the cavities. I guess I'm just going to have to graduate to aluminum molds. Thanks, JIM Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 28, 2008 Report Share Posted December 28, 2008 (edited) I solved the inconsistency by changing over to weight measurements. I weigh the plaster and water using a gram scale, the mix ratio for me being 5:4 plaster/water. The plaster edge will always turn up, unless you place the master in very late. But this can be difficult to time, impossible if you are making multi cavity molds. It is best to just accept the meniscus. After thoroughly drying the mold, remove the raised edges with a sheet of 300 grit emery paper, placed on a flat surface. The grit will clog and need cleaning several times, I find that air from the compressor is the easiest way to achieve this. Do not try the sanding process unless the mold is fully dried (30% - 35% of the demold weight). This flattened mold face will give a crisp mold line for future molds. It is a good idea to keep this first half and only use it for making new molds, using the 'new' mold to mold the second half. One reason for this, apart from not having to float the master again, is that all future molds will be bottom poured, thus eliminating the bubble problem, after a few taps etc. Dave Edited December 28, 2008 by Vodkaman Quote Link to comment Share on other sites More sharing options...
jimcline Posted December 28, 2008 Report Share Posted December 28, 2008 I solved the inconsistency by changing over to weight measurements. I weigh the plaster and water using a gram scale, the mix ratio for me being 5:4 plaster/water.The plaster edge will always turn up, unless you place the master in very late. But this can be difficult to time, impossible if you are making multi cavity molds. It is best to just accept the meniscus. After thoroughly drying the mold, remove the raised edges with a sheet of 300 grit emery paper, placed on a flat surface. The grit will clog and need cleaning several times, I find that air from the compressor is the easiest way to achieve this. Do not try the sanding process unless the mold is fully dried (30% - 35% of the demold weight). This flattened mold face will give a crisp mold line for future molds. It is a good idea to keep this first half and only use it for making new molds, using the 'new' mold to mold the second half. One reason for this, apart from not having to float the master again, is that all future molds will be bottom poured, thus eliminating the bubble problem, after a few taps etc. Dave Thanks again for the great advice. I'll keep working at it. Quote Link to comment Share on other sites More sharing options...
borderbasser Posted December 31, 2008 Author Report Share Posted December 31, 2008 Dave, I am not sure I quite understand what your last paragragh means. Are you saying that you remove the master and sand the mold face? If so, how do you replace the master and re-establish the seal between the mold and the master so that the next half of the mold doesn't find it's way in between the first half and the master. Thanks all for the replys. TJ Quote Link to comment Share on other sites More sharing options...
HJS Posted December 31, 2008 Report Share Posted December 31, 2008 Dave - My question is exactly the same as borderbasser. What do you do with the masters??? And also with the alignment devises??? I feel like you discovered a really kewl way to sidestep the bubble issue... but I'm not getting the entire picture. Quote Link to comment Share on other sites More sharing options...
Spike-A-Pike Posted December 31, 2008 Report Share Posted December 31, 2008 Dave - My question is exactly the same as borderbasser. What do you do with the masters??? And also with the alignment devises??? I feel like you discovered a really kewl way to sidestep the bubble issue... but I'm not getting the entire picture. HJS, Great idea... Dave, Can you provide a few pictures of your process? It may greatly simplify our learning curve. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 31, 2008 Report Share Posted December 31, 2008 This flattened mold face will give a crisp mold line for future molds. It is a good idea to keep this first half and only use it for making new molds, using the 'new' mold to mold the second half. One reason for this, apart from not having to float the master again, is that all future molds will be bottom poured, thus eliminating the bubble problem, after a few taps etc. Sorry, no pics. I am away from home at the moment, for another 4 weeks. After pouring and drying the mold, the master is carefully removed and the mold face sanded flat. No vent marks or location depressions, just a flat face. This mold half then gets sealed with 50/50 Elmers and water. No more than two coats should be required, as we don't need a shiny surface, just seal the mold and give it a bit more strength at the sharp corners. The master is coated in petroleum jel or a soft wax. This will solve the problem of liquid PoP seeping in the mold cavity. Next, the vent holes and location pins are added. These are formed from modelling clay. These will soften and even melt during the exothermal process, but this is not a big problem, it may stain the PoP mold locally, but this does not affect functionality. The mold face is also coated with release agent as above. The mold returned to the wooden mold box. Pour the second half. Take usual precautions to remove trapped bubbles. Using this new half mold, repeat the process above to make a matching half. Look after the master and the flat mold, for future mold making. This may seem like a lot of extra work, but it pays off when you want to make subsequent molds. Dave Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 31, 2008 Report Share Posted December 31, 2008 Another idea that I have tried and tested successfully, is a solution to problems encountered while floating the master, also removing the master. Instead of floating the master, the master is mounted on a cone of modelling clay, inside the mold box. The PoP is then poured. The master can still be adjusted to get the casting perfectly level. once the plaster is cured, the mold is removed from the box and the clay cone can be removed. Because the cone is bulky, the melting problem does not happen. The cone is removed very easily. This now allows you to ease the master from the PoP mold by pressing from behind. This works particularly well with wooden masters, as they can be tricky to remove without damage to the master or the mold. Dave Quote Link to comment Share on other sites More sharing options...
borderbasser Posted December 31, 2008 Author Report Share Posted December 31, 2008 Thanks Dave. I thought that was what you were talking about. I have a couple problems with that though. I have tried your method in the past, and it is very difficult at times to get the master back into the mold exactly as it was especially on moderately complex masters. To make things even worse, the bait has fins that are below the centerline of the bait that I would venture to say would be impossible to get back in place. The only option would be to cut that particular fin off before re-inserting the master back into the mold. The other problem is with the vaseline. Although it would work well I think, I have had problems with the POP picking up the brush strokes on the bait from brushing it on. Ofcourse, I guess you might be able to heat it slightly with a heat gun or hair dryer to melt it and smooth it out some. It would just take some experimentation. All and all, I think it is worth trying again. I think what I'm going to try first though is inserting a few wires through the center line of the bait and letting the wire extend out far enough out from the bait that the bait can be suspended over the mold box. Then all it would take is to fill the box up to the top with plaster and then lay the bait in. All should be well as long as the wires are straight and the pop is not so thick that the edges pull in, or not so thin that the pop rises up on the master. Sounds good anyway. And ofcourse if it doesn't work, I can pull the master and sand. Anyway, thanks guys. TJ Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted December 31, 2008 Report Share Posted December 31, 2008 The inside of the master cavity could be ground to suit, to allow a good fit. But if your master is so complex and/or difficult to remove, then maybe you should be using RTV. The PoP master described in posts 14 and 15, can just as easily be used to make subsequent RTV molds. Dave Quote Link to comment Share on other sites More sharing options...
