I've discovered recently that paint thinners can be used as a substitution to toner aide (toner darkener).

This DIY toner darkener costs 10x less than commercially available solutions and can hugely improve printed template contrast, for processes that use photoresist for image transferring, like printed circuit boards or T-shirt manufacturing.

You can watch my video or read this instructable below.

Supplies

- Any mild organic paint thinner (must contain a small portion of acetone).

Petrol-based paint thinners like white-spirit most likely won't work!

- Vellum paper ebay: https://www.ebay.co.uk/itm/50-x-A4-Vellum-Transluc...

You can also buy thick vellum paper from scrapbooking stores.

- Access to a laser printer

Step 1: Print Your Template

Step 2: Tape Down Your Template

The purpose of this step is to ensure that the template stays flat and won't warp.

It's better to tape it down to a cardboard. Less cleaning after spilled paint thinner :)

Step 3: Don't Use Toner Aide or Paint Thinner at All ... Well, Sort Of

Turns out, that you can use heat gun to re-melt toner on the paper and make it darker that way.

But it leaves visible lines from the printer, for better results we need to chemically etch a toner, proceed to the next step.

Step 4: Use Mild Organic Paint Thinner

Add a little paint thinner on top of the paper so it forms a small lake and let it dry.

If it didn't work as expected proceed to the next step.

Step 5: Troubleshooting

There are two possible solutions here:

1. Repeat previous step if your paint thinner is too weak. Maybe this one particular paint thinner won't work and you will have to try another one. Hopefully you can reuse it as a paint thinner :)

2. Paint thinner is too strong and dissolves toner immediately (acetone concentration is too high).

In that case you can dilute it with ethyl or isopropyl alcohol. Make sure to shake it thoroughly before use!