Tips: Silicone Rubber Molds, i have to remember my own tips XD

WARNING: Technical post, expect usual crabbiness!! :P

in a previous post here:


http://snowfern-clover.blogspot.com/2010/04/112-pastries-breads-danishes-i-dont.html


i related how i had to get a different sort of silicone rubber than the first time i bought them, in this post:


http://snowfern-clover.blogspot.com/2009/08/i-have-had-difficulty-sourcing-for-good.html

 being the semi-disorganized person i am (i refuse to outright consider myself disorganized, i know where everything is in this organized pile of mess!), i don't think i mentioned where i got the material from, or if i had, it's probably in my comments. so to those in Singapore, you can purchase 1kg portions from:


http://www.weeteetong.com/

directions to the place are in the website itself, and it's best you call the salesperson before heading down to, as i like to put it, "jalan ulu ulu". i'm trying to translate that phrase, best i can come up with is "middle of ****ing nowhere" :P i tend to exaggerate, i know :X

ANYHOW. before i start on my personal experience, if you're wondering where you can get more comprehensive knowledge on moldmaking, please please PLEASE go HERE:



http://www.hirstarts.com/moldmake/moldmaking.html

it has EVERYTHING you need to know, kinda sorta. i picked up whatever i know from that totally awesome site, and then wasted lots of material experimenting and adapting to local climates and conditions. so whatever i experience, please keep in mind that i'm in Singapore, and climate conditions definitely affect the pouring of silicone and resin etc since i don't have any of the funky machinery to help me remove bubbles and measure out the portions with extreme precision.

as always, proceed with caution, and i refuse to answer questions because.....hahaha i don't really pay all that much attention to what i do, this is my way of trying to REMEMBER what i did so i don't repeat the same mistakes again :( SUGGESTIONS ARE TOTALLY WELCOME THOUGH!!!!!!!!!!!!!!!!!!!!!! need all the help i can get....

Below are notes on RTV 589 vs RTV 585 (the first batch i purchased)

- RTV 589 is definitely softer and more pliable than 585

the catalyst is pink, so the resulting pour is a lovely strawberry yoghurt colour (i RIKES!). this is a good/bad thing, depending on usage. for recordkeeping purposes, i'm gonna flat out state that i would prefer 585 for larger, uneven items since i can stick in the clay and expect it not to distort that greatly. of course, if you use ADC, this wouldn't really matter. and either one for smaller resin pours. so for even larger food items, i probably have to stick to alley goop, which is a 2-part silicone putty and you can get that from clayalley.com. it cures firmer and faster than any silicone pour, although the learning curve is...a little trickier depending on the temperature of your surroundings and your hands. anyhow, that's another post for another day.

- take into consideration the size, detail and space between the items to be molded

i made the mold pictured above for 1:12 macarons, raspberries, eclairs, danishes etc, and in order to conserve on the amount of silicone pour used, i tried to squeeze in as many items as possible, into as little volume of mold as possible, but that also means that the mold itself is more flexible than if i used a larger container. and because i did that, i messed up my 1:4 and 1:3 molded items (not pictured), as i used the same container to make it. 589 was too soft for me to use polymer clay in it. i could have spaced the items a little better, resulting disaster is the price i pay for impatience and stinginess :P

- pick the right container

i used to use lego blocks, as suggested by the Hirst link i gave earlier, but after a while i've found it to be too much work for items that are so small. some japanese miniaturists i've seen use recycled milk cartons, properly cut and sealed with duct tape etc as the cartons are waterproof, and that's great and all, but again, i had plenty of sauce containers, and i tend to pick a clear container (this time, it was a PP  polypropylene plastic box from Daiso) since it's easier to see if there are bubbles trapped at the sides of the masters. i didn't choose a hard plastic in case the thing got stuck too firmly. ionos. the great thing about inverted sauce/takeaway containers too is that they are clear, and all you have to do is pop the lid off and push out the mold. naturally, i cut off part of the container to allow pouring. if you're confused about what i'm referring to, you can probably google for moldmaking with recycled margarine containres, plenty of resources out there (and probably where i got the idea from, but most likely cos i was lazy and just have too much crap lying around that i could use)


- make sure the items are properly adhered to the base of the container


if the master shifts during the molding process, not only do you 'lose' the item, fishing it out before the molding material hardens is a sticky and messy affair, and if you try and extract it -after- the silicone rubber has hardened, you risk ruining the entire mold, or the master itself. with a 1 pour mold, you could probably follow faithfully the steps suggested by Hirst, but i am always too excited to get it done that i hate too much prep work :X that's why i fail so much! LOL anyway.....

i had previously used double sided tape, that worked pretty well if you didn't care about the unsightly surface, and wanted a quick and dirty pour. well, i messed that up majorly with this pour :( i thought i hadn't mixed enough catalyst in, and so placed the poured mold near my laptop, which acts also as a heat source since this machine freaking heats up real fast even with the fan underneath it. i'm not sure where i got the idea that heat speeds up the process, but i think it stands to reason, after all it is an exothermic process, and the heat generated helps the rubber itself to cure. any physicists or chemists out there want to help me verify this? XD anyhoo, my point is, the double sided tape melted and created this gooey mess on the base/surface of the mold that try as i might, could not fully clean off. :( :( :( i took my blade and sliced off as thinly as possible the top layer, after scraping off whatever gunk remained after i let it soak in rubbing alcohol...alas, it is only marginally helpful, it's no longer that icky gooey and most of the glue residue was removed after 4 hrs of carefully cleaning (i really should try out the WD40 but ...the smell of that stuff makes me wanna puke) the surface, i gave up and prepared a new pour. i'll still use it though, for as long as i can tolerate the icky texture XD

- get the ratio right!

i think there's always an 'optimum' amount to mix such materials, like i've mentioned, the heat generated factors into the cure rate, not just the amount of catalyst. well, that's my opinion anyway for epoxy resin. but for silicone pour, i think it's even trickier, as soon as the catalyst comes into contact with the rubber, reactions start happening, gah! if you don't stir rightaway, or if the silicone rubber has been sitting around for a while (there's always a shelf life for silicone rubber/epoxy resin, as far as i know anyway), the resulting pour can clump up before you even attempt pouring :( the suggested ratio for 589 was 2-3% of the silicone rubber portion, but i think that's for amounts larger than 1-2kgs. for this pour, only approx 20ml was used!!!! i tried to play safe by keeping it to a 1-1.25% ratio for our climate, and oh boy, does temperature affect the pour. when i first tried out 589, Asuka was around to help me, and we were in my air-conditioned bedroom. that was a pretty successful pour, with the room temperature at approx 18-20 deg celcius. the weather this week has been hot and humid, and i don't usually work with the air-conditioner on, so i totally forgot to factor it in, and TADAH IT CLUMPED. i was frustrated, and thought back on all the possible variables since i kept the ratio the same, and so tried again today with the airconditioner on. PERFECT. no clumping. oh, and if you can, invest in proper measuring tools, my goal is to get an electronic scale.....soon...soon :( no place to keep my tools!!!!

- keep the stream thin while pouring, and TAP TAP TAP. this is to get rid of any bubbles that could have been introduced into the mix. i got tired of the tapping process, so recently i took to running an old epilator against my work surface (which is usually a box, to introduce further reverberation) LOL. don't judge me!!! i can't always have the washing machine running! XD and yes, the epilator is clean. :-/ freaking effective, just really noisy.....alternatively, you can place the container against a fan, which is what i used to do until i got this new table = no space for fan XD

- use wet wipes to clean up spillage

if any. XD

ok i'm sure i missed out other stuff, but this is a sorta 'newbie' post still, i'm still making mistakes and figuring out what i'm comfortable with....so remember, even if you fail the first time, you have to keep on trying!!! conditions of your environment are SUPER important when it comes to working with temperamental materials such as silicone rubber and epoxy resin!

comment if you've found this useful, or made it through the post without falling asleep ;) i know Asuka probably didn't even make it past the first paragraph ;P *snort*

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UPDATE!

the 2nd mold set BEAUTIFULLY i am SOOO pleased with it! so far, i've tested it with ADC and the results far exceed my expectations ^ ^

gonna update again with pics of some glasses and bottles woot woot!!!!