This guide documents the mold-making half of a year long art project between Andrew Quitmeyer and Madeline Schwartzman. This part of the guide teaches you how to rapidly create silicone and polyurethane molds in the field and replicate natural plant forms collected from all over the world as glowing, UV sensitive leaves. I have been interesting in non-(or less-) destructive ways of capturing forms in nature. I am also interested in doing it in mobile, very inexpensive ways.
This guide will let you know how you can recreate natural forms of 2- and 3-dimensional shapes with incredible quality and for VERY CHEAP. Hopefully by seeing how we made our large, interactive artwork, this how-to will help you with your art or science projects! We managed to capture forms of plants from places such as
- USA - East Coast
- USA - West Coast
- and more!
The other half of this artwork involves arranging all the leaves on a robot-converted dry cleaner that is controlled by special long-range RFID readers. You can see full details for how to make all that here:
If you want to learn more (especially on the philosophical / artistic side) about this artwork, and many more that were part of Madeline Schwartzman's "See Yourself E(x)ist" exhibition, you can see the manual here:
Step 1: Finding Leaves
Leaves are in lots of places! Go find em! The more you hunt for them, the more you start noticing all the different leaves around you! You get the "leaf-eyes" and suddenly start annoying your friends when walking around and stopping suddenly to look at a real cool leaf (or even start pulling out your silicone to mold right there!)!
Step 2: Theory: Rapid Cheap Flexible Quality Silicone Mold-making
There are tons of ways to make high quality molds of things, and they all have their various pros and cons.
The molds needed to be re-usable, and flexible (so that we could safely remove very thin, fragile, and delicate casts). This meant that plaster and other hard materials were not good for us.
For our project we wanted to create at least 100 unique molds. Many of the molds would be VERY BIG. This made using regular silicone casting (like you would get from Smooth-On) to be quite cost-prohibitive. We also want something we could potentially do directly in the field.
Eventually we settled on a cheapo, silicone caulk technique (like https://www.instructables.com/id/Worlds-easiest-si... ) except using Acrylic paint as a catalyst.
Theory Overview Cheap- Field Molds
There's lot of potential ways we can make our molds and our positives (or casts) for this project. It all depends on our goals and requirements.
Ideally if we had unlimited budget we would make lots of.molds out of high quality Platinum cure silicone (like “smooth-on” sells). Something like their “body double” silicone or their silicone putties would be great because you can work it by hand and it has releasing agent (oil) right in with it. Smooth on also has a type of silicone called “rebound” (they use “Rebound” Rebound® 25 silicone for a leaf). In general, smooth on has terrific documentation. They also have a hotline, you can just call them up an ask them questions. The downside is that the stuff can be pretty expensive. Something like a 30cm diamter lilypad could cost like 40+ Dollars in silicone to mold (and some time), and not every mold comes out good. High Quality silicone like smooth on sells is quite expensive in other parts of the world (like 1.5-2 times as expensive).
Silicone molds are nice in general because they are pretty re-usable, and can flexibly pull off of odd shaped materials (vs a rigid plaster cast). Also nothing really sticks to silicone (except other silicone), so you don’t hae to worry about release agents (as much).
Every mold you make will have its own peculiarities and challenges. Some parts will have weird gaps, or overhangs that can be hard to pull the model back out of the mold . Also if we are making lots of different molds for lots of different things we find, this can get expensive quick. Also if we are going to be making LOTS of these leaves, we will also be running into problems of having time and manpower to be mixing and molding all this stuff.
Cheap molding material High quality impressions with molding material (Can maybe even do the molding in the wild?) Cheap casting material Rapid manufacturing (or at least easy manufacturing / set it and forget it)
Step 3: Current Recipe
- Acetic Acid Cure Silicone caulk Clear (don’t get any other colors) (listed as GE Silicone 1, DON”T GET GE silicone 2)
- Acrylic Paint or Acrylic based “Fabric Paint”
- Baby Oil / Mineral Oil / Coconut Oil
- Dash of Corn Starch (optional, find it better without)
- Gloves (Nitrile gloves, or plastic gloves, cannot be latex gloves. Latex can mess with the silicone).
- Paper towels (disposable)
- Stirring sticks (Wooden popsicles that are disposable, or a metal stirring rod that you have to make sure to clean well after each use)
- Disposable mixing cups or bowls Wax paper or aluminum foil (to lay over worksurfaces)
Smooth Cast 326 Smooth-on
GLOW WORM (GREEN)
No Vacuum Chamber needed (e.g. https://www.amazon.com/Hydrion-Scientific-Chamber... )
Step 4: Molding Steps
- Clear out a workspace because stuff is going to get messy. Lay down some aluminum foil. Maybe oil it up with some mineral oil to help stuff not stick to the surface.
- Squeeze some of the caulk into a disposable bowl. For a glob the size of an apple add about 6 drops of paint.
- Stir the paint and caulk together well (the color will help you see if it is well mixed or not). Now you will have a sticky colorful thick paste. Our type of molding with this paste gets a lot easier if we can manipulate it with hands (or else you can squeeze and smooth it to ensure no air bubbles).
- Add 10 drops of baby oil for an apple sized glob. Mix it in well to your silicone. You will notice it getting oilier. Cover your hands with a little bit of baby oil to keep the silicone from sticking to your hands.
- Touch the silicone to see if you can touch it, and it has a playdough-like consistency. If it is still sticky, add in more baby oil. Grab a handful of silicone and knead it a bit to make it smooth and consistent.
- For a relief mold, flatten out your silicone into a kind of thick pancake. Press the object into the pancake of silicone. Rub on the silicone on the back, and the object on the front to make sure the silicone has nice and smooth contact with the object.
- Walls- Now if you have an open mold (like a relief mold). You need to add some walls to prevent the resin from spilling out when you are casting. Go around the whole border of your object and ensure that you have a least a 1 cm wall of silicone lip around the edge. The taller your wall, the more you can slosh around the epoxy you cast into it, and the less you have to worry about it spilling out. A tall wall can save material in the long run!
Step 5: Types of Molds
This is the main type of mold i have been making
This is where we just get about half an object. The half of the object can even have decent depth to it, but one half will always be flat (the side when we pour resin into the mold and is just exposed to the air). This is nice and easy way to do big, flat-ish things. A downside is that ,
Casting - Pour in
This is where we would just pour in epoxy into our releif mold as i have been doing. Works fine for flat things. 3D curves in leaves get a bit weird though, because parts that dip in will be thicker than parts that are flat in how the leaves were laying in the mold. Positives are that you can just pour stuff in, and let it set.
Casting - Spray On
In theory to make our releif molds a little more interesting and 3D, we could do spray on molding http://www.reynoldsam.com/product/ez-spray-jr/ . We could then make a normal relief mold, and then flex our silicone mold in any shape we want (like they do in the tutorial for concerete -https://www.smooth-on.com/tutorials/mold-leaf-casting-concrete/ ). Unfortunatley spray casting costs about 800-1000 dollars to get started .
Casting - Roto casting / Slush Casting / Jiggle Casting / Hula Casting / Sloshing it around
If you make the walls big enough on the edges of your leaves, you can put in a little bit of resin, and just slosh it around for 10 minutes or so until it gels up. This gives a more even distribution of the resin, helps make sure there are no thick spots, and uses less material. The cons are that it sucks up more manpower to be sloshing these things around, and you need to build high walls around your releifs to make sure it doesn’t spill everywhere. Here’s a video example of a person doing this https://youtu.be/bTP67mk3htI?t=361 .
3D -One part
Squish the silicone all around the object making sure there are no airholes. Determine what part of your object will be the “top” when you are pouring material in. Make a somewhat large hole there to pour resin into, and make some walls (or a type of funnel) shape to help pour stuff into it. Make another small “vent” hole in it to help pour material into it and let air escape. When it cures, you cut into in a bit with a razor until you can pull out the object.
You first mold half the object with a thick mold that you also make extra grooves and shapes in (as alignment holes). Then you let that cure and mold the other half of the mold onto it. I’m not sure this will work to well for very thin things like our leaves.
Step 6: Advanced Field Casting!
If you get really good, you might not need the lab any longer! You can go straight to nature and cast right off the tree! Just carry some
- Acrylic Paint
- Coconut Oil
around with you, and you are set!
Step 7: Casting: Making a Glowing Leaf Factory
After your early forays exploring nature, and getting good at molding are pretty settled, it's time to enter the industrial age. We had only a couple months left to make 1000 leaves, so we had to move fast and efficient. Get some tables, cover them with paper and foil to protect them from spills, and arrange your leaf molds so that you can mix and pour.
Do this A LOT
Our silicone molds can cast most materials except fancy “platinum cure silicone”. So epoxies and polyurethane resins all work fine! You might want to spray a light coat of oil (like pam) into the mold, and then brush it off with a paint brush if your molds keep sticking to the casts.
I have been using Smooth-Cast 326 “Liquid Plastic.” Smooth-on sells this, and it isn’t too expensive. It has a pot life of 7 mins, and cures in 45-60 mins. You can find other versions of smooth cast that cure in shorter or longer times.
For best results, I mix part b with some glow powder (bright green glow powder is the best and brightest and most reactive
Step 8: Notes and Tips
- Silicone Caulk (tin cure silicone) will prevent fancy “Platiinum cure” silicones from setting. So you can’t pour fancy silicone into a mold made from Silicone Caulk.
- Latex Gloves can stop silicone from curing Sulphur can cause silicone to not cure.
- You might notice your resin getting milky white-color near the surface, or lots of bubbles. This is a result of the silicone not being completely cured yet. Wash off your mold with some soapy water, and let it cure for like a day or so.
- Coldness, and high humidity can also cause the resin to get weird
Step 9: Testing: UV and Hanging Arrangements
For the best "pop" highlighting the fine details of your leaves, you want a really low wavelength (below 400nm, like 390nm). This reduces the amount of white light that get shined out by the light, and makes the light source to be not as distracting. The lights we found worked best were these:
Some of the glow powders we used were these:
When hanging the leaves you also need to find material that does not fluoresce. Some types of netting were too weak, or glowed brightly (even though under normal light they were clear). Some zip ties, and some hot glues fluoresce too, so watch out if you don't want those aspects to suddenly gain lots of attention. The net we used was from:
We drilled two small holes and passed very thin zip ties through the leaves to connect them with the curtains. We had to do lots of experimenting with different types of glow powders and different types of lighting.
Step 10: Bonuses: Embed Electronics and Sensors!
You can put wires and fiber optics directly into the molds. I made some capacitive touch-sensors with embedded LEDs and they were cool! as you approach, they light up!