Resin casting stuff...

[Starryeyes]

If that's the microwaveable , reusable mold making stuff yes I've tried it ... For my application I found that the composi-mold somewhat melted once I poured the 2-part resin in the mold and it starts to heat up.. I was able to cast the part but the results weren't as positive as I had hoped for... Prior to buying any I contacted the company and asked for a "sample" to test for them giving them positive and negative feedback ( good and the bad)...

[yekoms]

Thanks guys, I read some other review that were mixed. I figured that if heat melts it some resins would bother it. I'll stick with the good stuff. Thanks!

[wardster]

I just added a link to my last-before-this comment ... thought I'd mention it, in case what others (outside this hobby) have done interests you, Smokey?

[yekoms]

Back in my may 11th post I mentioned that the Smooth On Onyx resin didn't work to good. IT WAS MY FAULT not the product. I shouldn't have ASSumed that it was the product right away. I talked to the tech guys and he said that it sounded like it was not stirred or mixed enough. I mixed the next batch thoroughly it cast and cured just fine. The Onyx is harder than the 320 when it is fully cured. So far I do like the 320 better.

[wardster]

Ah, yes. Stirring! Lots and lots of stirring of the separate liquids, before combining them into one container, for pouring!

(Guess that's so ingrained a habit, now, that it didn't occur to me to mention it. Sorry!)

After watching some of the Smooth-On videos I had purchased on DVD, some longish time ago, I had put two old kitchen (butter) knives aside, just for that purpose -- one for stirring the liquid called "Part A," and one other totally separate knife for "Part B".

Further tips on knives used for stirring: use light weight butter knives! Gets tiresome stirring with heavy knives, after a while.

It's a good idea to mark which knife is which, somehow, too. One way is to drill holes into the handles: so that one hole means "Part A" and two holes means "Part B". The idea here being that you'll lower the odds of accidentally contaminating either container, with the wrong butter knife.

I actually keep a stopwatch with my resin casting tools and supplies. Makes it much more stress-free, to be able to time everything.

I find that it's next to impossible for me to pour small amounts, reliably, out of the containers the Smooth-On stuff comes in ... so, after three minutes of stirring Part A, I pour some of that container into a medicine bottle, that's much smaller in size. Then I can put the big container of Part A away; and can use the smaller container for my actual pouring and mixing chores. Holding the knife blade you used to stir the product with, in front of the big container's wide opening, helps to guide the liquid into the other bottle.

Ditto for Part B: three minutes of stirring, followed by carefully pouring some into a pre-labelled, smaller-sized plastic bottle.

One reason I'm using medicine bottles for my "ready service" containers is that a local dollar store sells some generic ketchup and/or mustard squeeze bottles, with great lids on them. The actual squeeze bottles are too large for what I want, but at only a dollar per squeeze bottle, I find it's well worth it to buy them just for the fancy caps. I put those caps on the pill bottles, instead.

I'll try to get some pics taken, a bit later on.

[Starryeyes]

Hey Wardster ! .. this is great reading!!... one thing I do with the large containers of product is remove the plastic lid, leave the aluminum seal on the jug .. then starting from the edge of the container just inside the lip I make a short pie-cut towards the center of the seal. I usually make the cut so when I lay the jug left or right that the small pie-cut is on the side.. I then bend the little flap down and control my pour.. once the pour is completed I flip the little pie-cut flap back up and place the plastic lid on for safe keeping .. the little flap stays intact because it's still glued to the edge of the opening... I have no problem making precise pours and it eliminates an additional container .. just my 2 cents ....

[wardster]

I'm diggin' reading your tips, too, Chuck!

I went through my plastic tote full of Smooth-On stuff, today, after reading your post above. Why? To see if I had saved any of the lids from old "Part A" and/or "Part B" containers. And yeah, I'd saved some. (Why? Who knows. But now, it's an advantage that I hadn't tossed them!) So now I'm thinking that I might modify some of my spare plastic lids to serve the same basic purpose you're talking about, above. That way, I can still cut most of the silver foil off of the top of new cans of resin ... but can still have that "ring" of foil on there, as a gasket (which is how I do things now) ... but would have the advantage of the small, controlled pour spout system you mentioned.

As for the additional containers ... photos will tell that story best, most likely ... but the "Part A" definitely "settles" a lot just from sitting, and I like to have a see-through container to tell me if the two separate components are pre-stirred enough ... so I'll be sticking with the secondary containers, for "actual use" purposes. Maybe it's just paranoia talking, but I take comfort in the idea of being able to look through the see-through containers, to make sure nothing has settled on me; and it's all pre-stirred enough. (Before I try mixing the two parts together, I mean.)

The biggest reason I'm using those smaller containers, though, isn't necessarily that idea above. It's partly carpal tunnel (big jars are harder on my wrists, if I'm using them a lot) and partly the idea that I'm mixing up VERY tiny batches of resin, at any one time. I mean, REALLY small. Like sometimes not even one of the smaller-sized gumball-machine containers full of either part; poured into (and then stirred together in) the larger-sized gumball machine containers. And to be able to do things THAT precisely, well, I know my limits; and being able to pour amounts that tiny, with that much control, seems like a job for the secondary containers I'm fond of.

Side note: one reason I'm using the bubblegum-machine "toy containers" instead of "normal cups" or whatever, is that I can clean them out, and keep reusing them. Regular rubbing alcohol on a paper towel works wonders. I get a LOT of use out of those toy containers, before they're too old and crudded-up; and have to be retired.

More later ... but I'm learning stuff from you guys ... and hopefully I'm throwing out a few worthwhile ideas, here or there, too!

[yekoms]

I'm diggin' all of these tips and learin' a bunch of stuff... Thanks a bunch and I hope that others are readin' this thread. I have more questions...the only problem I've been having occasionally is a bubble or two on the bead of a wheel. That is the bottom of the mold (where the resin runs to first) with the back of the wheel being the top of the mold. I'm getting more familiar with the whole process so I think that I just need to slow down on my pour, pour a little and move the mold around to fill that area first.

[wardster]

Have you tried injection? Rather than a straight "gravity pour"?

If not, you may want to see if a local pet supply store (or similar) has the kinds of medical-style syringes you see on TV all the time in hospital shows or whatever... but without the actual needle portion. (I'll try to get some pics of what I'm using, before too long.)

Basics of it is: you mix your resin, like usual, but instead of pouring it in and hoping gravity will get it to where it needs to go, you "suck up" the mixed resin into the syringe (out of whatever your mixing container is) ... and then, literally inject the resin into your mold. Probably works best in situations where there's a specific entry point, and one or more "vents" to let air out of the mold. You could always cut in such entry / exits holes, in a pre-existing mold, if they're not there already. Pushing a piece of brass tube through the mold makes a round hole. I use that trick a lot, for areas where air needs to vent, and air pockets always form.

(Just a thought!)

[wardster]

Other things to try:

If you're using a one-piece mold, that's sort of "bathtub shaped" in a sense, and bubbles or voids form on the bottom parts of the mold / top parts of the casting made in it, you may want to pour as usual ... and then (gently!) poke at that area of the mold, after the pour but before it begins setting up. You can try a toothpick as your poking tool ... or an opened-up paper clip. Just enough to pop bubbles; but not enough to harm the mold. That sometimes helps to cut down on the amount of bubbles like you described.

Have you ever used talc or baby powder as a mold release agent? I feel it's a big improvement over liquid forms of release agents. (Even the best stuff. Even when brushing it on, instead of spraying it on.) The liquid stuff tends of add too much unintended "texture" to a carefully prepped surface, for my taste. The clean-up hassles, post-casting, are virtually nonexistent when using powder versus liquids ... and it seems like I get much better "contact" between the mold's surfaces and the actual resin. Etc., etc.

[yekoms]

Ward and others thank you very much for your input on this forum. The other day I saw a video on Smooth On's website and they were usin' a syringe to inject resin. I didn't try it yet. For now I concentratin' on the build and I'm not casting anything at the moment. I don't use release agents at all as the Smooth On tech advised me not to use them. As he said just a thin film of petroleum jelly on the silicone of a two piece mold when make in the second half of the mold is all that I have ever done. I haven't had any resin castings stick to silicone at all.

[wardster]

That syringe trick kicks butt ... but is mostly useful for two-part molds; especially those that have been set up for that process.

Some of the molding-and-casting projects I'm doing right now, just won't cooperate at all with a straight "gravity pour" situation, with anything resembling a successful casting ... but the syringe trick makes that process work out just fine. That and setting the molds up for syringe "injection" right at the start. I'm really happy about having had some good success with the syringe process, because it opens up a lot of possibilities for casting stuff, that just wasn't going to work, any other way.

Like all of us here on these forums, I'm just learning as I go -- reading a lot; trying stuff; watching helpful online videos, etc. -- but if I were to try to summarize one of the main challenges with casting I'd say that getting resin into a mold is sometimes no big deal. It's getting the extra air that's trapped in a mold, OUT of there, so you don't have spots where there are problematic "voids" or areas on the casting that have lots of bubbles, etc., that might become a major pain! (Or even make your final castings unusable.)

The syringe trick, when used along with thoughtful two-part (or occasionally more than two-part, in some cases) mold design, helps avoid that sort of a major problem with "voids" in a mold. Air has to get out of a mold. It just has to. And that takes planning.

From everything I've read / seen online in videos / and found out by first-hand experience, I'd say that it's a valid assertion to say that the more "enclosed" a mold design becomes, and the smaller the pre-made mold cavities are (the shaped holes that the resin has to get into), the harder it will be for air to find a path OUT of a mold, so that casting resin can get INTO that part of a mold.

And what I'm seeing, first-hand, is that in those situations, using even just a little bit of added pressure or "push" helps. A lot!

I'll see if I can't dig up some oldies-but-goodies, in terms of articles I learned a lot from, in back issues of FineScale Modeler or what not. A professional model maker by the name of David Merriman once wrote a few articles for them, on the subject of casting -- and his articles were (I thought, anyway) much more advanced than many I've read in hobby magazines. One article in particular, by him, showed diagrams and what not of how he designs his two-part molds. He has a sprue or gate or whatever, going downwards in the mold ... but not leading directly into the bottom of a cast resin part, like a waterfall. His gates or sprues or whatever, go down from the top of the mold, turn so the channel is going horizontally (where it may keep going, horizontally, if he has more than one small part he wants to make) ... and then come up from UNDERNEATH the individual casting cavities, where the parts are actually formed ... and fill up the spaces for the resin to go, from the bottom up -- forcing air upwards, as the resin enters each new part of the mold -- and finally, there are some escape channels for air to come out, on the upper sides of each of the parts he's trying to make.

Why so complicated? Because he's casting up things like periscopes, for submarine models ... and there's just no way you'd reliably get good castings, with such thin-walled parts, if you were doing something like pouring resin in from the topside; and hoping air will get out of the mold, from the bottom up -- while resin is coming in, and is trying hard to trap any bubbles moving upwards. Since air bubbles are likely to want to move upwards, anyway, he took advantage of that ... and had the resin enter from the bottom side.

So, in cases like that: resin is entering from the bottom of a mold cavity, and fills the cavity, from the bottom up. Meanwhile, as resin is entering, air is being forced upwards, out of the mold.

This makes for a complicated-sounding mold design ... BUT ... in actual use, it's quite simple to make castings. You just begin to pour or inject resin into the designated entry hole; and keep applying steady / gentle pressure, as you continue to put the mixed casting resin into the mold via that hole; and keep an eye on the vent holes. When you see resin start coming up out of the series of air vent holes or channels, then you know everything inside the mold got filled, so you stop pouring or injecting resin into the mold.

He's also doing stuff most of us can't do -- (like "vacuum degassing" his mold rubber, after he mixes it but before he uses it; or putting his freshly poured molds-and-resin into a "pressure pot" to crush any remaining air bubbles) -- but the principles of good mold design still apply.

The reason I brought up talc or baby powder is for molds designed sort of like what he's using. With thin-walled castings, which have small air vents, you're going to have a lot of tiny passages for resin to get in, and for air bubbles to try to escape from. Liquid mold release agents, if used in excessive amounts, might clog your air vents ... causing major problems with air bubbles and voids.

David's required parts were flat; so he had two-part "flat" molds much like those for injecting styrene into metal molds. His air vents were, therefore, located between the two halves of the mold itself. Open the mold, and the parts / sprues / etc. all come out as one "flat" piece. So yeah, he could skip using mold release if he wanted to, with such parts. (I'm not sure he does, though. He's doing production casting, in a sense -- with dozens of "shots" required -- and needs his molds or "tools" to last as long as possible.)

One of my current casting projects has a shape that isn't flat, at all ... so the mold design on that one took much more planning than I'm used to, with other castings. I ended up actually having to make a three-part rubber mold; with unusually-located air vents, to make that mold work. I have air vents puncturing the rubber molds, as it were. So, I'm putting baby powder all over the innards of my molds, so the parts will release without any problems ... but I'm especially using that powder in those small air vents! I needed some kind of a way to make sure the cast resin, in those vents, was not going to try to stick to the rubber itself, and rip my molds up!

Anyway ... just sharing some of my casting experiences, and thoughts on the process. And am continuing to enjoy hearing about other's experiences, and what works for them.   (Thought for admins -- any chance this thread might be better seen by others, if it was moved over into the "tips and tricks" section?)

[Starryeyes]

Yep ... Good call Ward... As soon as I get a chance I'll move it to the "tips" area.. So if you don't see it here you'll know where it ran off to !!

[Fletch]

This book has everything you need to know from sculpting your own monster figure all the way to casting it then painting it. I got it so I would have some sort of idea how to make my own monster to fit in a hot rod. Now I just need the time. This book is perfect if you want to know a whole lot of info on this subject.Attachment Deleted

[Starryeyes]

Jun 24, 2015 18:58:25 GMT -5 Fletch said:

This book has everything you need to know from sculpting your own monster figure all the way to casting it then painting it. I got it so I would have some sort of idea how to make my own monster to fit in a hot rod. Now I just need the time. This book is perfect if you want to know a whole lot of info on this subject.View Attachment

This is something on my bucket list to attempt...,thanks for the info Fletch!