Dave stared at the magical canvas in his possession. It had managed to eat his hand, turning it into a two-dimensional drawing and it had caused the portrait to fuse with his wrist. Fortunately, yanking his hand out had fixed the problem, but it had caused a good number of questions to pop into his head. His most burning question was, what were the limits?
He took a cup off his table, then slowly inserted it into the empty canvas. Like his hand, it was consumed, creating an ink drawing of the cup as more of it was pushed in. He pressed the cup even deeper, until the canvas enveloped it completely. He brushed his hand across the flat surface. The material felt too thin to be paint, and it was almost chalky, like it was done with pencils. More interestingly, his hand didn't go into the painting like last time.
Slightly confused, Dave decided to test something. He pulled out his wallet, then pressed it onto the canvas like he had done with the cup. This time, the wallet simply sat at the surface, as if the painting rejected the item. It seemed like no more than one real-world object could be placed into the canvas.
He returned his attention to the cup. Now that it was completely in, how would he get it out? It wasn't an extension of him like his hand was. He absentmindedly drew a star on the cup using a spare pencil, hoping that it might give him inspiration on how to fix this. After a Placing his palm flat against the image of his cup, he felt something beneath the surface respond. He moved his hand downward, trying to force this new feeling to follow it. The cup remained under his moving hand. He then willed it to return to his open hand, and he felt it materialize and push him away from the surface. The canvas allowed him to control whatever was within it, to some degree. He removed the cup entirely, leaving him with an empty canvas once more. As he looked it over, he realized the cup now had the exact same star that he'd drawn onto it.
Next, Dave grabbed a paint brush. He attempted to paint on the canvas, but the material kept eating his paint brush. He attempted with a pencil next, but it was the same outcome. The pen was no different as well. He'd hoped he could just paint things and make them real, but it appeared like the painting needed to have something real in it before he could draw or modify it.
He cast a sideways glance at his modified cup. His change had been small, but how big of a change could he make and still pull out? After scrounging about his room for something he would definitely not miss, Dave found a penny and threw it into the canvas. He then took a spare eraser, and tested to see if he could erase whatever pigment this painting was using. Surprisingly, this was even easier to erase than regular pencil-work. It took a single stroke to wipe out half the penny.
Pulling the penny back briefly to see if he could, he found that the blurry, erased portion quickly gained definition as it was extracted, leaving Dave with a near-half penny with a very strange cut line. As it was all but worthless now, he returned it to the drawing, then erased it completely. As the final bits disappeared, he could feel his grasp on the object disappear as well, until there was nothing. He tried to draw the penny back, but the canvas had once again began to eat his drawing utensils before they could make a mark on the page. It was unnerving to know the canvas could destroy what was put in.
His next "victim" was a bunched-up tissue from his waste basket. Upon placing the trash into the canvas, Dave took a few moments to lightly sketch a cup around it. As he drew one line after the next, the painting seemed to understand his intentions, and magically pulled the sketch together until it looked like a cup with a picture of trash on it. The same happened with coloring, as well. Small gaps between strokes or instances of color bleed seemed to fix themselves as he made the cup a vibrant shade of pink.
The drawing was more or less complete for his purposes, so he removed the object to see what would happen. A plastic cup with an absurd drawing was his reward, which was confirmation enough for him. This painting could change one thing into something completely different.
Dave looked over the painting. He'd gained some more knowledge, but he wasn't sure if he should continue, or how. He needed to see if he could create a living thing, or make something alive, inanimate. What would happen if he completely changed a living thing into some other animal? Would it remember what it originally was, or have a new mind fitting for the creature that was made? How would modifications on living pieces work? Should he test on himself, someone else, or maybe he should buy a pet or grab a spider or something outside? Maybe it'd be wiser to try and convert trash into gold, diamonds or cash.
After some thought, Dave decided to...