Restoring classic cars can be a difficult business. As a car gets older, more of its component parts start to degrade, and more of those same parts go out production and become harder to find. For example, if you find yourself trying to restore a Jaguar XJ6, you might have cracked or broken taillight lenses, with replacements virtually impossible to come by. But what if you could remanufacture a fresh set yourself?
If you want to go that route, you’d need a very particular set of skills. YouTuber Eric Strebel is lucky enough to have those in spades. As an industrial designer, he runs Botzen Design, and he’s got plenty of experience in producing prototypes and design concepts in all kinds of plastics. His YouTube channel has a wealth of information regarding resin casting techniques, explaining in simple details how to achieve the best possible results. It’s those very skills that he relied upon for this project.
Strebel took on the job for a customer, who sent in a pair of two-tone taillight lenses in amber and red, taken from a Series 2 Jaguar XJ6. His plan was to recreate fresh lenses using resin casting techniques, albeit in a monochrome, all-red version.
Incidentally, if these seem familiar, it might be because our own Jason Torchinsky did a big deep dive into Jaguar taillights quite some time ago. His history lesson taught us that originally, U.S. market XJs started off with all-red taillights, later switching to a version with an amber section at the top. Then he found an ultra-weird all-amber version with a red bulb behind it. In any case, Strebel’s effort is about creating an all-red taillight, but you could use the same technique to do amber instead if you so desired.
The first job is to create a set of molds of the taillight lenses, so they can be recreated in resin. This is achieved by making a silicone casting around the taillights to copy the geometry. This is done in two halves, creating a mold that can be filled with resin and then pulled apart once the material has hardened.
Scanning the taillight on a flatbed scanner provides an accurate outline of the part which is used to create a “splitter board” on a 3D printer, along with flexible seals using TPU filament. Strebel then inspects the lenses, deciding on where he’ll set up a fill port and vents for his resin casting molds. Getting these details right is key to ensuring the molds fill evenly with resin without any air pockets that could spoil the finished product. An old shelf donates the wood for the mold box, which fits around the 3D-printed base.
Each taillight lens is prepped by having its weep hole sealed with clay, with white PVA glue applied to stick it to the splitterboard. With the wood box, splitterboard, and taillight assembled, Strebel then pours silicone over the top to create the first half of the mold. The silicone was degassed in a vacuum chamber first to remove all the air content for the best possible results. The worktable was also vibrated during pouring the silicone to further remove any bubbles remaining.
Once the silicone has cured, the mold boxes are disassembled. The 3D-printed splitterbox and flexible seal are removed while leaving the lens itself in the silicone. This allows the second half of the silicone mold to be poured over the top directly, creating a perfect two-part mold. But first, Strebel glues lengths of copper wire all over the lenses to act as vent holes. 3D-printed spouts are also added to block out space for pouring resin into the finished mold. With a touch of release agent in the right places, the assembly is then ready for pouring silicone for the second half of the mold.
Once cured, Strebel is left with two halves of a silicone mold in the exact geometry of the Jaguar taillight. He notes that getting the molds perfect is important for a part like this, as poor surface finish or air bubbles would ruin the translucency of the part.
Finally, it’s time to actually make some new lenses. Before pouring the resin, the silicone molds are first warmed to 110 F to help the resin flow nicely. Strebel then mixes up a BJB Water Clear resin, chosen for its good results for translucent and transparent parts. A colorant is then added to get that rich red color so typical of vintage taillights. The resin is then degassed before pouring into the left and right lens molds, each sitting at a 30-degree angle to aid filling and resin distribution. Once full, the vent holes bleed resin, making them look like some kind of kooky Halloween decoration. The parts are then cured under heat and pressure in a sealed tank, which helps shrink any remaining air bubbles to be as tiny and invisible as possible.
After setting overnight, it’s time to unmold the finished products. “Oh, looks fantastic, very, very, juicy,” says Strebel. “Like candy, blood candy.” The parts have excellent translucency, looking like they just came off a production line in 1974. The silicone molds did an excellent job of preserving the shiny surface finish and the dimpled construction which spreads the light from the bulb. They’re a near-perfect color match, too.
Cost-wise, how does it shake out? “You’re looking at anywhere from $1,000 to $2,000 for something like this,” says Strebel, noting this includes labor and materials. It’s a steep price to pay for taillight lenses, but the results are exemplary.
For the deeper dive, I asked Strebel if he could tell us about what it would take to reproduce the two-tone design. “It’s totally doable, similar to the way the part is made for production, you would need to make one of the colors first then insert it into the master mold and cast the other color next to it, it’s just a matter of time and cost,” he explains.
The process is fiddly, but once you’ve got the molds, you can make more than one set of taillights. “You can get about 20-30 parts from a good silicone mold, says Strebel. “Then the mold will begin to show some wear and the parts will not be 100% any more.”
The technique is slow and time intensive, and few of us have the money to hire an industrial designer to produce replica parts for us. However, if you’re building a classic and you absolutely need an obscure variant of an old taillight? Well, this is how it’s done.
Image credits: Eric Strebel via YouTube screenshot