16 replies to this topic

[Darkdragon]

Ok. The collaboration Channel posted a video few days back explaining how to make silicone tips for stefans. I followed the steps flawlessly but seem to have a problem.. My dart tips are still tacky and sticky after a day and a half left out to set. The only notable difference in my procedure is my mold ; I drilled out the shape of the domes in my wood, and smoothed them out using a ball grinding bit on my dremel...The mold looked perfect before I tried using my silicone, so Im stumped. I used 100% silicone. Was I supposed to use that acrylic & silicone mixture stuff or am I retarded? Would using wood instead of a plastic affect my silicone? ( Wood is a porous material and I was wondering if it had any effect on it allowing my darts tips to dry / cure.)

Edited by Darkdragon, 17 May 2014 - 07:58 PM.

[Mully]

Give it more time to cure.

[Thorn]

Depending on the humidity near you, the silicone could take anywhere from 24-72 hours to fully cure. Also, I do think the porous wood is affecting the silicone. I recently did pretty much exactly the same thing, making a mold with wood, and after leaving it out for two days it still wasn't cured. However, when following the exact same procedure with 1/2 HDPE, it worked perfectly. I would suggest making a mold from HDPE, or just using a polyethylene cutting board. Hope this helped.

[Darkdragon]

I see. Thank you both, I will give it more time to cure, and what exactly is HDPE?

EDIT
Google answered my question about high-density polyurethane.

Edited by Darkdragon, 17 May 2014 - 08:49 PM.

[Thorn]

I see. Thank you both, I will give it more time to cure, and what exactly is HDPE?

EDIT
Google answered my question about high-density polyurethane.

Glad I could be of help. Also, it's actually high density polyethylene. The part number for the HDPE on Mcmaster is 8619K431 for 3/8th inch, and 8619K471 for 1/2 inch.

[KaneTheMediocre]

You can use 100% silicone (which is totally not 100% silicone) just like you did, and given enough time they should cure. I don't expect that a wooden mold would cause your problem. Just wait a week with as much free air as possible.

[mysterio]

In addition to all these things, adding corn starch to your mixture in order to get a quicker cure time. The more you add, the faster it cures, but it will also end up being firmer the more you add. Doable, but only if your local rules allow it.

[shmmee]

There are two types of silicon caulk. One cures by absorbing moisture - the other cures by releasing it. The type you want cures by absorbing it. I'm going to look in my crystal ball and predict that you've used GE II brand silicone or some other "low odor" silicone caulk. Thoses types cure the wrong way - by releasing moisture.

Go to Wal-Mart, look for a opaque tube with black printing - it will be the cheapest tube on the aisle most likely and buy it. That's the stuff you want. It looks like this (without the purple glove - that's just saving the unused caulk)

Edited by shmmee, 18 May 2014 - 01:11 PM.

[orangeparkour]

Here in Wisconsin (which I have to assume isn't too much different than Michigan) my silicone domes take a solid 2 days to cure in their molds, unless it is full on summer with High humidity, which neither Wisconsin or Michigan has yet. Also, if you made your dome molds too deep, those are going to take longer to cure as well.

[shmmee]

Here in Wisconsin (which I have to assume isn't too much different than Michigan) my silicone domes take a solid 2 days to cure in their molds, unless it is full on summer with High humidity, which neither Wisconsin or Michigan has yet. Also, if you made your dome molds too deep, those are going to take longer to cure as well.

The right kind of silicone at the right ratio of corn starch and silicone can cure enough to unmold in a few hours. Too much corn starch can make heads very firm, that can be countered by mixing in mineral spirits.

[Darkdragon]

You can use 100% silicone (which is totally not 100% silicone) just like you did, and given enough time they should cure. I don't expect that a wooden mold would cause your problem. Just wait a week with as much free air as possible.

*Fan girls over getting a response from Kane the Great* ...Well, its been 5~ days and they are finally starting to firm up. And I put them outside too, for "free air" lol.

In addition to all these things, adding corn starch to your mixture in order to get a quicker cure time. The more you add, the faster it cures, but it will also end up being firmer the more you add. Doable, but only if your local rules allow it.

Id rather it be as soft and rubbery as possible. I'll be using these darts on little kids and older dudes alike.

There are two types of silicon caulk. One cures by absorbing moisture - the other cures by releasing it. The type you want cures by absorbing it. I'm going to look in my crystal ball and predict that you've used GE II brand silicone or some other "low odor" silicone caulk. Thoses types cure the wrong way - by releasing moisture.

Go to Wal-Mart, look for a opaque tube with black printing - it will be the cheapest tube on the aisle most likely and buy it. That's the stuff you want. It looks like this (without the purple glove - that's just saving the unused caulk)

Oh. Shoot, I'll have to try that stuff out. I had no idea, and what youre saying makes a lot of sense. Lets just say for a moment that it is the wood being porous that slowed down the cure time so much. The type of silicone that absorbs moisture should preform the opposite of the other type in my wood mold, correct?

Here in Wisconsin (which I have to assume isn't too much different than Michigan) my silicone domes take a solid 2 days to cure in their molds, unless it is full on summer with High humidity, which neither Wisconsin or Michigan has yet. Also, if you made your dome molds too deep, those are going to take longer to cure as well.

I dont think they are too deep, in fact, I didnt think they were deep enough. And it been a bit humid in my area the last 2 days haha

The right kind of silicone at the right ratio of corn starch and silicone can cure enough to unmold in a few hours. Too much corn starch can make heads very firm, that can be countered by mixing in mineral spirits.

Paint thiner counteracts the cornstarch? Interesting.

[Exo]

It's just a matter of moisture. The cornstarch acts as a curing agent, so a chemical that has the opposite effect will act as a counter-balancing agent.

For tip making, I'd advise you go with Oogoo (shmmee's formula of Walmart sili +cornstarch). I've made some VERY MASSIVE objects out of that, and they've cured in just hours, given enough cornstarch.

[shmmee]

Oh. Shoot, I'll have to try that stuff out. I had no idea, and what youre saying makes a lot of sense. Lets just say for a moment that it is the wood being porous that slowed down the cure time so much. The type of silicone that absorbs moisture should preform the opposite of the other type in my wood mold, correct?

Correct.
The type you're using probably cures by releasing moisture. Putting it in a some what air tight mold, mixing moisture laden corn starch in with it (more moisture the silicone needs to disperse to cure) and expecting it to cure efficiently is like putting a cap (or a rubber banded finger from a glove) over the tube. It's holding in the moisture, and preventing the cure process.

The mold porosity and ambient humidity honestly has no impact on the cure time if you're adding corn starch to the right kind of silicone caulk. The corn starch is simply a vehicle to disperse moisture evenly through the silicone so it can all cure at once instead of slowly sucking moisture from the surrounding atmosphere. I've used wood to make experimental forms out of. The porosity impacts the surface finish of the dart head, (the reason I favor HPDE cutting boards for molds) but did not affect cure time at all. And like exo - I've also made large baby food sized blocks of oogoo. Such a large volume should of taken weeks to fully cure - but the corn starch cured it over night. It's not the mold but the ingredients.

I'd be interested in seeing the mold design you're using. Glory1610 and I are still actively developing metal free darts. Current experiments involve replacing felt tips with dryer lint to improve hopperability and production rate. Initial tests are very good, but who knows how the lint will hold up over time.

Edited by shmmee, 22 May 2014 - 01:31 PM.

[KaneTheMediocre]

I think the simplest technique for getting soft rubber tips is to not add anything to the silicone, and wait for it to cure. I've heard a lot about absorbing moisture vs releasing moisture. I'm sure it's true in ways I don't understand because I'm not a chemist, and probably much more relevant if cornstarch is used. All of the silicone caulk I've seen/used has cured by releasing vinegar ions--a process that requires the presence of moisture, but doesn't (as far as I can tell, with my super-molecular-vision) to involve it moving into or out of the silicone.

It is definitely the case that adding corn starch makes it harder, and mineral spirits makes it softer, but once you get into that you lose the convenience of squirting your goo directly out of a caulk gun. I wouldn't go so far as to say these additives aren't useful and helpful in many cases, but I'd advise against messing with them until after you've gotten the process working with just the silicone.

Also, I sell the HDPE dome molds (8x8 sheet for $15) if you're interested, but I don't have any reason to believe that theres anything wrong with your woooden mold. E-mail kanethetoymaker@gmail if interested--my PM box is perpetually full.

[Darkdragon]

I think the simplest technique for getting soft rubber tips is to not add anything to the silicone, and wait for it to cure. I've heard a lot about absorbing moisture vs releasing moisture. I'm sure it's true in ways I don't understand because I'm not a chemist, and probably much more relevant if cornstarch is used. All of the silicone caulk I've seen/used has cured by releasing vinegar ions--a process that requires the presence of moisture, but doesn't (as far as I can tell, with my super-molecular-vision) to involve it moving into or out of the silicone.

It is definitely the case that adding corn starch makes it harder, and mineral spirits makes it softer, but once you get into that you lose the convenience of squirting your goo directly out of a caulk gun. I wouldn't go so far as to say these additives aren't useful and helpful in many cases, but I'd advise against messing with them until after you've gotten the process working with just the silicone.

Also, I sell the HDPE dome molds (8x8 sheet for $15) if you're interested, but I don't have any reason to believe that theres anything wrong with your woooden mold. E-mail kanethetoymaker@gmail if interested--my PM box is perpetually full.

I very well may be contacting you about the mold, but my dart tips finally cured and I'm going to attempt later to get them out of the wooden mold and if its successful and not too messy then I may just continue using my own but were you talking $15 plus shipping or 15 shipped?

[cheerios]

I very well may be contacting you about the mold, but my dart tips finally cured and I'm going to attempt later to get them out of the wooden mold and if its successful and not too messy then I may just continue using my own but were you talking $15 plus shipping or 15 shipped?

$15 plus shipping.

[Darkdragon]

Correct.
The type you're using probably cures by releasing moisture. Putting it in a some what air tight mold, mixing moisture laden corn starch in with it (more moisture the silicone needs to disperse to cure) and expecting it to cure efficiently is like putting a cap (or a rubber banded finger from a glove) over the tube. It's holding in the moisture, and preventing the cure process.

The mold porosity and ambient humidity honestly has no impact on the cure time if you're adding corn starch to the right kind of silicone caulk. The corn starch is simply a vehicle to disperse moisture evenly through the silicone so it can all cure at once instead of slowly sucking moisture from the surrounding atmosphere. I've used wood to make experimental forms out of. The porosity impacts the surface finish of the dart head, (the reason I favor HPDE cutting boards for molds) but did not affect cure time at all. And like exo - I've also made large baby food sized blocks of oogoo. Such a large volume should of taken weeks to fully cure - but the corn starch cured it over night. It's not the mold but the ingredients.

I'd be interested in seeing the mold design you're using. Glory1610 and I are still actively developing metal free darts. Current experiments involve replacing felt tips with dryer lint to improve hopperability and production rate. Initial tests are very good, but who knows how the lint will hold up over time.

If you are still interested, I can give you a pic of my wooden mold. The tips didnt come out well, as they stuck to the wood almost 80% of the time. I wound up using a cutting board made of HDPE. That worked a lot better, and I may consider now commisioning out my tips, they turned out PERFECT.