If you don’t know Sugru, you are missing on one amazing DIY material: it’s like playdoh putty in consistency. It sticks to many materials like glue and dries out in 24hrs to a robust, yet flexible silicon rubber. It’s great to fix stuff around the house and hack things together that to adapt your environment to you and not the other way around.

A quick search on the web will show you the amazing hacks that people around the world create with Sugru. As I mentioned earlier, Sugru is like playdoh in consistency and the most common handling is to mold it with your fingers. Probably one issue I see in many fixes using Sugru is that the finish still preserves the fingerprints and the shape resembles those early childhood creations.

In this entry, I’m going to show you an easy technique to replicate existing shapes, so that your Sugru fixes look as good as the original, without fingerprints or wobbly surfaces.

A while ago, my favorite mug broke.

Got shit done

Got shit done

I bumped it on the ground and “I Got It Done” indeed.

I couldn’t let it be. This mug was my inspiration and not to mention it had already a Sugru magnetic hack to keep the spoon in place.
I glued back the large pieces, but there was an important piece at the border missing. “I can probably fix this with some Sugru” I thought, but I was not going to get the curved smooth surface with my finger molding skills.

So, I decided to make a mold for the missing piece, with the intention to press the Sugru in shape.

The first step wast to take an impression of the internal cylindrical shape. I used playdoh putty (yes!) and molded it in the inside of the mug to capture the shape.

Putty in the inside to have a print of the internal curve

Putty in the inside to have a print of the internal curve

Then, I sticked this shaped putty on a part of the border that was still intact.

Creating a mold of the border

Creating a mold of the border

This prepares the backing for the mold.

Next, I mixed some quick-setting gypsum and poured it on top of the putty that we have prepared in place. I strengthened the plaster with a cotton net, in the same way doctors make a casting around a limp when you break a bone. This prevents the casting from breaking when removed.

gips on the mold

gips on the mold

Once the gypsum was dry, I removed it from the “source” and placed it at the side of the fracture. Note how sharp is the internal border. This will give us a clean edge to drink from the mug.

gypsum casting removed

gypsum casting removed

As Sugru sticks to almost every materials, we need something to prevent it from attaching to our casting. The most common release agent for Sugru is soapy water, but the gypsum absorbs it immediately, leaving a dry surface for Sugru to stick to. With some experimenting, I used a silicone grease. Vaseline should also work.

gypsum cast for sugru

gypsum cast for sugru

Now we are ready to fill the crack with Sugru. I used pitch-black Sugru to match the color of the mug. It took a bit of pushing and playing with the mold to shape the Sugru in place.

Mug is back in service

Mug is back in service

The border is perfect but the pushing in place left some marks on the final molded Sugru. Still far better that anything I could do by molding it with my fingers.

(… and in case you are wondering what is that funny protrusion on top of the handle, it’s a magnet in some Sugru to keep a spoon in place. The shaping of the handle  is part of the previous Sugru hack this mug had undergone. You can see why I could not just throw it… too much Sugru invested in it 🙂 )