DIY An Instant 1/2 Rd RTV Silicone Mold For Under A Buck.

[Husky]

Very nice!!!!!!!!!

Husky...I have looked in Walmart, Home Depot, and Lowes........Cant find Mainstays product. I see DAP brand but there are 20 diferent types. Most say they have phenol or some other crap in them. Is that the same stuff? or is it 100 percent silicone? Do you think brands sold for use in fishtank sealing are equivelent?

Sonny, The ACE store by me only sells one kind of DAP in wh, blk and clear, so I can't tell you with any certainty, which one, as I don't have a tube in front of me, presently.

Mainstay is a WalMart brand and, here in NH, it's in the paint section with all the other Caulks, right under where the D2T used to be!!

Edited July 18, 2009 by Husky

[Piscivorous Pike]

Husky, this will illulstrate post #29, this is the 1st and 2cd molds I made with this home made quick vulcanized rtv:

The model is imbedded in clay, electrical wires mark vent paths

CLICK ON THUMBNAIL TO LOAD BIGGER BETTER PHOTO

This is the completion of the first half, clay removed, notice when I set the model into the clay I first heated the edges with a torch lighter to soften the clay, it brings the oil base to the surface.

CLICK ON THUMBNAIL TO LOAD BIGGER BETTER PHOTO

And finally (the color is due to the leaching from the model)

I have not fired up my microwave and plastisol yet but I filled the trout with DWP and cast a solid FISH with the mold just to check out what it would produce. I have no doubt these will work. My next one is a jerk bait with hook slot. I must imbed a metal plate in the mold.

Edited July 18, 2009 by Piscivorous Pike

[Piscivorous Pike]

Thanks again Husky. If thinning the Wally RTV does not work, the next mold I will make will combine your two systems:

Your suggestion, this link, post #3:

http://www.tackleunderground.com/forum/hard-baits/15486-rtv-alternatives.html

I saw this idea before you posted it but forgot about it.

Skinning the project and making a thin layer of rtv building up two sided molds can take advantage of your quick set Mainstay accelerated RTV.

Combine the two.

Looks like this may be the most economical RTV I can get that will cast the plastisol.

John Greer- Silicone Mold Making Rubber, RTV Molding Rubber

looks about 1/2 cost of all oth

ers at least. Anyone know where I should look for more comparisons of pricing?

Example:

This rtv cost $56 for 4.4 lbs. I used 4 tubes of main stay to make each of two two piece molds, they cost $12.

They amount used is about 1 pound per tube, or 4 pounds per mold. If I used the JG RTV that would be a cost of $56. I saved $44 or 79% . The Mainstay molds cost 21% of the JG mold would.

If I skin it and use an outer layer of JG RTV I estimate the mold would use 10% of the good stuff and cost. $5.60 + $10.80= $16. 40.

So for $4 to %5 more I can have a top grade mold. The Mainstay accelerated by water can be poured or trowlled into the skinned RTV mold.

Wow, Husky has improved the skinning process by figuring a way to thin out the Wally World Mainstay RTV. My wife thinks I am working on the home improvement projects today. It does look that way but... I will report back after I complete this next mold!

[Husky]

Thanks again Husky. If thinning the Wally RTV does not work, the next mold I will make will combine your two systems:

Your suggestion, this link, post #3:

http://www.tackleunderground.com/forum/hard-baits/15486-rtv-alternatives.html

I saw this idea before you posted it but forgot about it.

Skinning the project and making a thin layer of rtv building up two sided molds can take advantage of your quick set Mainstay accelerated RTV.

Combine the two.

Looks like this may be the most economical RTV I can get that will cast the plastisol.

John Greer- Silicone Mold Making Rubber, RTV Molding Rubber

looks about 1/2 cost of all oth

ers at least. Anyone know where I should look for more comparisons of pricing?

Micro Mark has a decent 1 to 1 RTV that sells for $30 for 2 lbs.

Example:

This rtv cost $56 for 4.4 lbs. I used 4 tubes of main stay to make each of two two piece molds, they cost $12.

They amount used is about 1 pound per tube, or 4 pounds per mold. If I used the JG RTV that would be a cost of $56. I saved $44 or 79% . The Mainstay molds cost 21% of the JG mold would.

If I skin it and use an outer layer of JG RTV I estimate the mold would use 10% of the good stuff and cost. $5.60 + $10.80= $16. 40.

I found that many commercial molds are over built. If you have 1/4" covering the deepest part of the model, you have enough. If you are using cheaper sealant and use a bit more, no harm no foul, but if you are using an expensive RTV (Like Dow Corning 3120 which I use for casting metal,) it's just wasteful, IMHO.

So for $4 to %5 more I can have a top grade mold. The Mainstay accelerated by water can be poured or trowlled into the skinned RTV mold.

Wow, Husky has improved the skinning process by figuring a way to thin out the Wally World Mainstay RTV. My wife thinks I am working on the home improvement projects today. It does look that way but... I will report back after I complete this next mold!

Thanks for the input.

Edited July 19, 2009 by Husky

[Sonny.Barile]

The John Greere website listed a "silicone oil" thinner on the price list page.

[Piscivorous Pike]

It is amazing how one member can affect the methodology of another. I have changed everything because of Husky's contribution.

I tested the two two piece molds. They were made with supporting plywood on each half. I used my $5 injectors on both. $5 plastic injector! But found if using injection I like Vodkaman's vacuum reverse injection better.

I had a slight problem with one mold that led to a discovery that improved everything. A bubble under the skin of the impression would expand when hot plastisol was injected and cause a deformity in the casting. I slit it open and put RTV into the bubble under the surface of the impression, smoothed it out with a finger and then a wet finger and got a fix.

I found that these RTV molds are spongy. If I just filled the cavity with molten plastisol and then pressed back and forth I could burp the air out of the trapped detail and get a smooth casting. No hassle just burp it. The molded in vents work well. My POP and DWP molds of the same model need to be injected, they will not fill by themselves.

Could not be easier, I put a rubber band or two around the mold, fill it burp it and once it sets dump the critter into cold water.

I can put up my injecters and vacuum cleaners now.

Next I can experiment and see if I can build my most difficult 5" jerk bait (TU taught me this, its long, pics too.), it has thin flukes at the end of a narrow 3 " tail and also hook slots. A brass bar with a cross piece soldered to it to anchor it in the rtv will complicate making the mold just a little. Hope I can thin the RTV like Husky taught me and avoid the liquid RTV as a skinning step. I will check in when done.

[Vodkaman]

PP, Interesting read.

If the RTV is spongy, you may be adding too much water, it takes very little for the reaction to take place.

Dave

[Piscivorous Pike]

PP, Interesting read.

If the RTV is spongy, you may be adding too much water, it takes very little for the reaction to take place.

Dave

Dave,

I think the spongyness, and it isn't too much, is from the air that gets into it even though I mix it in a vacuum bag. It is quite firm but has enough give that I can make the liquid plastisol in the sprue dance up and down but not spill out. That is enough motion to work the air out of the small tight spots that are at the end of flukes or fins. That is a lot less hassle than filling injectors or hookingup shop vacs. All the jerk baits I cast have those appendages. One in paticular is a 7.5 inch reaper another one has flukes at the end of a long skinny tail which is difficult to feed platic down to get enough pressue to clear the fluke. I have to push the air out vent in the end of each tip of the flukes.

The air bubble I outlined in the RTF are the result of the mixing. That is why I skin the model, I am satisfied with the surface of the casts. None of these are saleable. Done for my own fish catching so the quality although poor for human consuption, is ok for fish!

The Vodkaman vacuum injection is great on casting the plastisol at a low temperature and that keeps the color I work most with from changeing, bright flo pink, pinker than bubble gum. If it gets hot it turns to bubble gum color. Injection does not work at that temperature because it begins to set in the injectors. I think this burp method has a possiblility of using a lower color friendly temperature.

It has been fun, and since it is a hobby and I am not worried about P&E sheets I am likely going to buy the commercial RTV, what price is fun? This mixed water accelerated RTV is quite right to fill the back side of the molds and be more economical on the expensive RTV.

I like to tinker, so this was a very educating experience.

[Vodkaman]

PP, I understand now. That is a very good solution, compressing the mold to aid flow into the difficult areas.

I plan on using a combimation of vacuum and injection at the same time, if the injection does not do the job on its own. For the injection, I will use a cake syringe. Cost a dollar and easily dismantled for cleaning. I have used the cake icing syringe before, when pouring thick resin/microsphere mix for hardbait bodies.

Dave

[Sonny.Barile]

My Walmart now has the Mainstays clear. $2.97 US I will be fishing on Saturday and cultivating ideas on Sunday. Sounds like a great weekend to me!!!!!!

[Husky]

Today, I made a mold of a VERY complex critter using this method, and it came out perfectly! I'd post a pic, but it is for a "Client" who asked that it remain unseen!

The detail is comparable to the "Expensive Spread".

[Piscivorous Pike]

I poured up a couple in my now complete molds and I am not too happy with them afterall. The joint between the two halves, remember I made 2-piece molds, allows flashing.

My thin tail shank with a fluke jerk bait does not pour with the squeeze it method. It will take injection. I find that messy. So I am going to build a DWP again with Vodkaman's suction injection as before but now I have a better idea, to use a manifold on a 4 gang mold. It should work very well having worked with the prototypes already.

This method of using the silicone is ideal to use as a filler with twp part RTV. I can make as I said a two piece mold with the silicone and two part RTV for about $16.

Using the two part RTV will make a good two piece as it will flow and level out where as this water accelerated silicone is not very viscous, it is more like a putty so it does not flatten well at the joint line on the critter.

I bet this silicone is very good on one piece molds. My 1st halfs of the ones I cast are very good.

[Sonny.Barile]

Husky

What paint thinner did you use? Not being a chemist I would like to make sure I use the same stuff as you have already done it and youre still alive....LOL

Was it Walmart brand?......right near the caulking shelf?.....about $4?

BTW I have a master paddle tail swimbait made from hard plastic and I am going to build a polymer clay one peice mold tomorrow. This will be my hard mold for the silicone casting. The lure is designed with a flat top to facilitate one peice pour from the top construction......(just like youre worm molds) and the sides are tapered sort of acting like a draft angle for easy demolding.

Sonny

[Husky]

Husky

What paint thinner did you use? Not being a chemist I would like to make sure I use the same stuff as you have already done it and youre still alive....LOL

Was it Walmart brand?......right near the caulking shelf?.....about $4?

BTW I have a master paddle tail swimbait made from hard plastic and I am going to build a polymer clay one peice mold tomorrow. This will be my hard mold for the silicone casting. The lure is designed with a flat top to facilitate one peice pour from the top construction......(just like youre worm molds) and the sides are tapered sort of acting like a draft angle for easy demolding.

Sonny

The One I have only says Recordsol Paint Thinner on it. It doesn't list the ingredients.

It says General Purpose Thinner and Clean Air Solvent on the Bottle.

[Husky]

I

I bet this silicone is very good on one piece molds. My 1st halfs of the ones I cast are very good.

Good point as this method was Originally Conceived for 1/2 Round, IOW One Piece Molds.

BTW, if the model has a lot of fine detail, it helps to put a quick thin application of the Silicone directly on the Model before "Squishing" to catch all the details.

That's what I learned at Hammer Mechanic School this week.

Edited July 30, 2009 by Husky

[stephanec12]

First off, I don't know whether to thank you guys or curse you. I stumbled onto this site a while back, and am a hopeless bait making addict now, thanks a lot.

On to the subject at hand.

I've been playing around with Husky's method for a couple weeks now. Took me a while to find a Silicone that would water cure, Wally world doesn't carry a house brand up here in Canada I finally found one that works last week.

I too am trying to create a two-part mold, stick baits to be exact, and I think I've figured out an easy method.

First I made a small cone out of pink insulation board and glued it to the nose of a senko.

I made a mold form out of foam insulation board as husky described. Filled it with half a tube of silicone mixed with water, as per the instructions i've read here. I then placed my Senko in the silicone with the cone against the wall. I then filled the mold with the other half a tube of silicone and compressed the whole mess with a piece of insulation board I had removed to make the form.

When its all cured I had a Senko encased in silicone. With a long and very sharp blade I made an incision along the side of the block, going as deep as the bait locked inside ( which was dark, makes seeing it through the silicone much easier). The incision ran from the mid point of the bait all the way to the end of the mold where the foam cone was. This incision allowed enough opening to remove the bait and cone.

And voila, I have a stick bait mold. Just wrap an elastic around the upper part of the mold to hold the incision shut. Use the hole the cone made as a pour hole, and I'm in business. There is a little bit of flash from the incision site, but thats only 1/4 the flash you'd get on a fully two piece mold, and it doesn't seem as severe either. I'm just making baits for personal use so for me flash isn't an issue.

I'm not sure how this method would work with more complex baits, but for more symmetrical baits with no appendages, flukes and sticks, it is pretty easy and foolproof IMO.

Thanks again to the people of this community, and Husky for letting us in on this awesome method.

[Piscivorous Pike]

That is a well known method to make a two piece mold, but because of the features on my model I cannot cut and split the mold. My tail section is too thin, I cannot place the tape.

One way to help you make that cut I have read is to place clear tape along the edge you would wish to split the mold at. Then mark the edge of the tape with a black marker. You can see that through the translucent silicone, You cut to the black edge and naturally the silicone molded the seperation in at the tape.

I think this link shows how to do this:

Moldmaking With Clear Rubber at Freeman Mfg. & Supply Co

Edited July 30, 2009 by Piscivorous Pike

[Husky]

First off, I don't know whether to thank you guys or curse you. I stumbled onto this site a while back, and am a hopeless bait making addict now, thanks a lot.

On to the subject at hand.

I've been playing around with Husky's method for a couple weeks now. Took me a while to find a Silicone that would water cure, Wally world doesn't carry a house brand up here in Canada I finally found one that works last week.

I too am trying to create a two-part mold, stick baits to be exact, and I think I've figured out an easy method.

First I made a small cone out of pink insulation board and glued it to the nose of a senko.

I made a mold form out of foam insulation board as husky described. Filled it with half a tube of silicone mixed with water, as per the instructions i've read here. I then placed my Senko in the silicone with the cone against the wall. I then filled the mold with the other half a tube of silicone and compressed the whole mess with a piece of insulation board I had removed to make the form.

When its all cured I had a Senko encased in silicone. With a long and very sharp blade I made an incision along the side of the block, going as deep as the bait locked inside ( which was dark, makes seeing it through the silicone much easier). The incision ran from the mid point of the bait all the way to the end of the mold where the foam cone was. This incision allowed enough opening to remove the bait and cone.

And voila, I have a stick bait mold. Just wrap an elastic around the upper part of the mold to hold the incision shut. Use the hole the cone made as a pour hole, and I'm in business. There is a little bit of flash from the incision site, but thats only 1/4 the flash you'd get on a fully two piece mold, and it doesn't seem as severe either. I'm just making baits for personal use so for me flash isn't an issue.

I'm not sure how this method would work with more complex baits, but for more symmetrical baits with no appendages, flukes and sticks, it is pretty easy and foolproof IMO.

Thanks again to the people of this community, and Husky for letting us in on this awesome method.

Thanks for the feedback. I'm happy that you found the subject useful. If you have pics, I'd love to see them, as many others here might, as well.

BTW, Giving Credit where it's due, albeit a bit tardy, I believe Jerry Redg8r posted the process of making a silicone "Clam Mold", years ago, which is where I originally found out about the water curing of Silicone.

[Husky]

I've been hit with one reoccurring question;

How much water?

To assure an even and sufficient mix:

There is no specific ratio as the silicone will only take on a certain amount of moisture. One good way to apply the water is to spray it over the silicone, mix it in then do it again. Moisture is what causes the Sealant to cure but there is no prescribed ratio. Spraying the water gives a better chance you'll get a good, even mix.

And that's what I learned at Hammer Mechanic School.

[Piscivorous Pike]

This suggestion was made in this thread and it worked, I made several molds this way.

I took my vacuum food sealer and made a pouch/bag and put in the amount of Walmart silicone I was to use, carefully putting it at the bottom so not to trap air.

I then filled the bag with water and then poured the water out. What remained as droplets in the bag was sufficient.

Next I vacuum sealed the bag, removing the air from the bag using the wet fast setting and holding the manual button down to get it good and tight drawing the air out.

I kneaded the package after sealing it well, this mixed the moisture and very little air as there was hardly any in the bag.

Cutting a corner off the bag allows you to use it like a chef's pastry bag and squeeze out the RTV. I used a straight edge on a flat surface to get the last drop of it.

[Gator44]

Adding water to silicone for a fast cure is a huge advance in mold making technology and I can't thank those who shared the info enough.

However, a word of caution for those who a using the silicone in home workshops as I have found that the acetic acid fumes given off by the silicone even long after it has cured are HIGHLY corrosive. Cast iron surfaces such as table saw tops are especially susceptible and can rust badly overnight. Make sure your shop tools are protected with Boeshield or some other rust preventative, keep your molds is sealed containers, and remove waste from the shop.

[Piscivorous Pike]

Adding water to silicone for a fast cure is a huge advance in mold making technology and I can't thank those who shared the info enough.

However, a word of caution for those who a using the silicone in home workshops as I have found that the acetic acid fumes given off by the silicone even long after it has cured are HIGHLY corrosive. Cast iron surfaces such as table saw tops are especially susceptible and can rust badly overnight. Make sure your shop tools are protected with Boeshield or some other rust preventative, keep your molds is sealed containers, and remove waste from the shop.

Yes!

My molds have hook slots which were made using pieces of brass shim stock which from your local hardware is available in various widths, thickness and lengths.

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The acetic acid while curing really coroded some of these. Copper turned blue, brass turned green!! I now coat them with protecting grease or vaseline for storage while the molds are relatively new.

Aluminum and copper are available too. Very little work involved to make a blank this way. Just stick it into the model and pour RTV, POP or DWP around it. For POP and DWP I have also used a dremel and cut a groove for the shim and epoxied it in later.

http://www.ksmetals.com/index.html

I wonder if the aluminum would be more resistant to the acetic acid?

[irbassnut]

Hey!

Thanks for the tip,Tried my 1st one today .

Came out perfect ,even better than the

$38.00 RTV I've been buying.

Can't wait to get back to Wally World !!!

It was only $2.47 for the tube

Thanks Again

Ray

Tombstone Baits:)

[irbassnut]

Hey!

Thanks for the tip,Tried my 1st one today .

Came out perfect ,even better than the

$38.00 RTV I've been buying.

Can't wait to get back to Wally World !!!

It was only $2.47 for the tube

Thanks Again

Ray

Tombstone Baits:)

And here it is !!!!

Worked Great!!!

[Piscivorous Pike]

And here it is !!!!

Worked Great!!!

very good, smooth and shiny! How did you get your finish so smooth? That is a problem for me, I have difficulty with the RTV H2O accelerated with some bubbles. I had been cautiously coating the model with a skin coat before filling the mold with the RTV when making a new mold.

What is your procedure? Thanks in advance.