I previously mentioned that commercial fudge is made on a slab of marble, but I used a Pyrex bowl. I also tested a modified recipe on friends and the best comment I got was that it was like frosting. It was very rich and I had to keep it on ice on hot days or else it turned to mush. I tried making it in a steel bowl and that failed. Blobs of milk fat separated from the candy. It didn't taste right and it looked awful. It took me two weeks to figure that one out.

If you remember your chemistry, this is an example of primary nucleation. The super saturated solution forms crystals based on contact with the surface of the container and the texture of the surface absolutely affects the crystals produced. Polished steel: bad. Polished glass: okay.

All the videos I found showed fudge shops that used a marble slab as the surface to make the fudge. Polished marble is obviously not the same grain as polished glass and I wanted to see the effect. I didn't have time to play games with it while the Farmer's Market operated.

Now I do.

$50.00 polished marble table:


It would have been less but I had to buy screws.

Fudge made on the marble slab:


It made a huge difference. Now I have to teach myself to anticipate when it hardens so I can cut it before it sets.

Recipe:

3 cups gran sugar
3/4 cup heavy cream
3/4 cup whole milk
3/4 cup semi sweet chocolate chips
1 1/2 ounce light corn syrup
1 tablespoon butter
1 teaspoon vanilla
1/4 teaspoon salt

Cook it on low heat and stir it until the chocolate melts and the sugar dissolves. You can't leave sugar granules in the mix or else they seed the mix and turn the batch into a bowl of chocolate flavored sugar. Clean the inside of the pan with a wet basting brush and make sure you clean below the top of the mix. Don't worry about the water. It will boil off.

Heat to 240 F and test for soft ball stage.

I let it cool in the Pyrex bowl for half an hour before I poured it onto the marble, then flipped it with the spatulas. It's very different from the glass bowl fudge I made last year.

If you're wondering, the marble slab is 20" x 25" and I paid $30 for it from a local counter guy.

What it looks like if you don't clean the sugar crystals off the inside of the pot:

Your link is broken.

I always thought they made fudge on marble because they could keep the marble cold.  Good to know.  Thanks for posting, OP.

Link fixed.

The screw up picture is also primary nucleation. It happens when some sugar granules don't dissolve. They seed the mix and cause it to form table sugar size crystals. That batch was a liquid when I turned off the heat.

I'd like to examine a couple of batches with a microscope to see if I can see the crystals at optical magnification. An answer to that question has interesting possibilities.

I also bought a coffee grinder to powder the chocolate chips. Powder cocoa is 150% to 200% of the cost of chocolate chips. I'm sure I could use less of it due to the density, but I'm not sure it's exactly the same stuff. Powdered foods sometimes use additives so they don't turn into a big blob. It's probably something simple like lecithin, but I already tested the mix and found that 10 ml of corn syrup plus or minus makes a big difference. Yes, I measure the corn syrup with a beaker. I used to use a measuring cup, but I got inconsistent results.

that is interesting, didn't know any of that.

The coffee grinder made it much more consistent.