Introduction: McRib Is Back...FOREVER. (Preserving Food and Polishing Epoxy)

By Narwhal Labs
About: Narwhal Labs is a community and makerspace that encourages and supports creative building, learning, and experimentation.
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The McRib (was) back, and we wanted to preserve it for generations to come. This started as a fun project idea, but when we got to the drive through window and learned we got one of the last McRibs available this year - it got real.

While we'll do our best to keep this Instructable informative and educational, our video below is riddled with jokes and we had a ton of fun making it - we'd appreciate if you could check it out.

Supplies

Step 1: Prepare a Mold Box

Step one is to prepare a basic mold box. We'll be using this to cast our food item in.

We have a full parametric mold model for Autodesk Fusion 360 available free on our github page and attached here. You can also use a tool like makercase to auto-generate vectors for a box.

We laser cut the box, and assembled it with Sci-Grip Weld-On 3. Please wear an appropriate respirator and check the SDS before using Weld-On 3 acrylic solvent. We then sealed the outside edges of the box with hot glue to prevent epoxy leakage. The box was waxed with a mold release wax so it comes out easily. Other mold release sprays may work fine.

Attachments

Step 2: First Epoxy Pour, and Sealing the Food

Fill the mold box with about half an inch of epoxy. While TotalBoat ThickSet's low viscosity makes it easy for bubbles to escape, we put it in a pressure pot, pressurized up to 45-50PSI for some extra insurance. You'll want to leave it to cure for about 24 hours until it's mostly cured.

Don't forget to mix your epoxy for at least 3 minutes, scraping the sides and bottom as you go. Transfer it into a second cup (without scraping any remaining epoxy out) and mix for an additional minute to be extra safe - this is known as double mixing. This is pretty basic, but if you need help calulating the volume of epoxy for the pour, there's a handy calculator here.


For sealing the sandwich, we mixed up some high performance epoxy and brushed it on all of the surfaces of each sandwich component. We then placed it on a silicone mat and into our makeshift low-temp oven for about an hour, which holds at about 115 degrees F (46C). This extra step is unnecessary, but it accelerates the curing process.

Step 3: Epoxy Barbecue Sauce

This is getting absurd, but absurd is what we do.

Water content can interfere with epoxy curing, so we made sure to order the McRib with no sauce. We improvised and used epoxy with pigments and some coffee grounds to make an epoxy "barbecue sauce" to paint on the McRib.

With the sauce on, it was time to assemble the sandwich with its onions, pickles, and buns. We placed it back in our low temp oven so we could continue the project in just a few hours.

Step 4: Final Epoxy Pours

We did our final two epoxy pours with TotalBoat ThickSet. Each pour was about an inch thick. Each one was cured in the pressure pot to eliminate the appearance of air bubbles. To minimize the appearance of layers, we poured the second pour after the first was in a gel state - after about 12 hours. The whole mold was rocked side to side to encourage air bubbles trapped in the sandwich to escape. We made sure there was enough epoxy resin to cover the whole sandwich with a little extra headroom. Once we got it as air-free as we could, we placed it back in the pressure pot at 45-50psi for the last time and let it cure for the weekend.

Step 5: Sanding and Polishing

Right out of the mold, things were looking pretty good, but we really wanted to punch up the clarity of this casting.

We dry sanded the block on all sides to get it flat up to 600 grit, and continued to step through the grits with wet sanding all the way up to 1200 grit.

Once flat and wet sanded, it's time to polish. Using a DA polisher or some drill polishing pads, apply a buffing compound. We used TotalBoat TotalBuff. Automotive buffing compounds will work fine if you have them on hand. We followed up with a high shine polishing compound - TotalBoat TotalShine for a crystal clear finish.

This process is long and requires patience, but it's totally worth it.

Step 6: Admire Your Hard Work.

You've worked hard. You came, you saw, you put a McRib into a block of glue. You sanded your fingertips off and have polish sprayed all over your workshop.