These are all hand-painted material studies from my GAM 233 class back in 2018. Each week we had a set of 4-6 materials and were tasked with painting them in the form of cubes using Photoshop.
Transparent Studies - Stained Glass, Amber, Glass w/ Whiskey, and Ice
Fabric Studies - Leather, Denim, Cotton, Burlap, Satin, and Wool
Dirt and Foliage Studies - Grass, Dirt, Snow, Sand, Ground, and Asphalt
Household Studies - Wicker Basket, Candle, Garbage Bag, Cardboard Box, Yarn, and Blanket
Stone Studies - Obsidian, Concrete, Worn Stone, Limestone, Marble, and Granite
Metal Studies - Painted Metal, Gold, Aluminum, Chrome, Rusted Metal, and Iron
Wood Studies - Walnut, Pine, Natural, Decayed, Painted, and Burnt
Food Studies - Apple, Chocolate, Cheese, Bread, Meat, and Strawberry
Organic Studies - Dust, Cloud, Fire, Sponge, Green Slime, and Lava
Synthetic Studies - Rubik's Cube, LEGO, Rubber Eraser, Kneaded Eraser, Clay, and Play-Doh