Buying silicone and resin in bulk and how to use it efficiently?

[Kominyetska]

1) I'm looking to ramp up production on some colored keycaps so I need materials (silicone and resin). I can keep buying "trial" sizes or go "pro" and get gallon buckets. I'm curious to hear from established artisan makers about the volume of materials that you guys purchase. Are you buying 1 gallon at a time or maybe 5 (or more)?

2) When you're dealing with gallon buckets, how do you measure out what you need (since you're likely only mixing a few Oz per part for small molds or maybe a few dozen)? Do you have a bottle (like the trial size) that you keep replenished for easy pouring?

Any insight into the high-volume mold and casting process would be very appreciated.

Thanks!

[Sneaky Potato]

Just get some smaller containers and fill them as needed. I use ketchup-type bottles for my resin, but they're not actually condiment bottles. They seal well and make dispensing easy.

As for silicone, you can find containers that are similar in size to the trial size bottles, and just fill those as needed.

Silicone is the biggest pain in the ass when trying to transfer to a new container, but having a second person helps. You can always pour it into a big plastic mixing container, and then pinch the edge for more accurate pouring into the smaller container.

[OfTheWild]

Just get some smaller containers and fill them as needed. I use ketchup-type bottles for my resin, but they're not actually condiment bottles. They seal well and make dispensing easy.

As for silicone, you can find containers that are similar in size to the trial size bottles, and just fill those as needed.

Silicone is the biggest pain in the ass when trying to transfer to a new container, but having a second person helps. You can always pour it into a big plastic mixing container, and then pinch the edge for more accurate pouring into the smaller container.

Yeah thats why ETF does too with the condiment bottles. Do you mix your colors in with part A or part B for longer term storage? Does it keep well that way? I've been just doing single batch mixes so I haven't needed to do something to be uniform across many pieces yet.

I kinda wish there was something like a giant refillable caulking gun for the silicone.

[Sneaky Potato]

I mix colors into part B and store them if needed. I've been told they will theoretically stay good for the entire shelf life of the opened resin, but colors that contain white will see a lot of settling at the bottom and require lots of mixing (sometimes with a tool to free up the color from the bottom). I usually mix up enough color for all of the keys at once, keep the majority of the resin in a large sealed container (or several), and then pour it into dispensing bottles or cups as needed.

Resin doesn't really store all that long once opened, so I wouldn't recommend buying the larger containers of it unless you're positive that you'll need it. I started with only using the trial size bottles and medicine cups because they were easier to manage, but now I just went through a few gallons of resin in a couple of weeks. Only buy what you'll use, as it's easy to waste it if you're not careful.

Silicone can be a pain to work with, but just be patient and stick with the trial sizes until you're doing some serious silicone pouring. Those smaller bottles are easy to handle and store.

[Leslieann]

For mixing, buy a postage scale, it will make your measurements more precise.

[Kominyetska]

Great info. I think I'm ready to buy by the gallons, but just wanted to make sure I wasn't missing anything in terms of pouring and storage. Thanks!

[bmmcwhirt]

There shouldn't be any issue buying whatever amount you feel comfortable paying for. As long as you only mix what you need for the moment the stuff can sit around for a while. You can also use the calculator on the Smooth-on page: https://shop.smooth-on.com/    click calculator at the top.

Also the postage scale is a very good idea as measuring cups markings are very imprecise.

I also tell anyone casting to read the info on Hirst Arts. Most all of it is good no mater what material your casting in.

Basic
http://www.hirstarts.com/casting/casting.html

Advanced
http://www.hirstarts.com/casting/advanced.html

Plastic/Resin
http://www.hirstarts.com/casting/plastic.html

[sinusoid]

Watch out for the silicone, some brands don't age well, and you won't be using a lot of it.
I learned my lesson the hard way, had to throw away a half of a 5kg bucket.

Resins are sensitive to moisture, ESPECIALLY polyurethanes. Limit their exposure to air humidity. Don't keep the containers open unnecessarily. Spray them with lighter butane, canned air, or CO2 just before closing the container. Those gasses are heavier than air, they'll displace it in the container, limiting amount of air humidity that could come into contact with the resin during storage.

Keep them away from high temperatures. Store them in a ventilated area. Especially the polyurethanes, because of isocyanate sensitization (look that up).

In general, calculate your batch sizes, timelines, match them to order volumes, and try to use up your stuff quickly. Do as little storage as comfortably possible.

For mixing, I suggest calculating the volume from mass/density (check datasheets), and doing volume based mixing, unless you're comfortable with shelling out north of $300 for a good grade used laboratory scale. Measuring by weight is more accurate only if you have a precise scale, and they don't come cheaply.
I suggest using math+physics and syringes instead.

I kinda wish there was something like a giant refillable caulking gun for the silicone.

There you go.
The general practice to keep them clean is to use a foil bag. Put it inside, and pour the silicone into it.
If you have a compressor, there are pneumatic versions as well, they do the squeezing for you.
You can also get a pressure paint container with a bottom drain, pour the silicone in, clamp a valve on a hose, pressure it up, and you're good to go. Make sure you have a dehumidifier, or use preconditioned gas (like CO2 bottles).

What used to work for me in the past was to store the silicone in plastic bottles (think coke/pepsi) upside down. Open the cap, squeeze out as needed.

Have fun! 

[Kominyetska]

sinusoid, thanks! That's all really useful info.