Electronics > Manufacturing & Assembly

Sodium Hydroxide or PhotoResist Developer and Drain Cleaner

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I need some advice in making some Positive photoresist developer.

From what I can find a commercially bought Photoresist developer contains around 5% Sodium Hydroxide (shown here) which has to be diluted with 4 parts water. (as detailed here).
Now I have some drain cleaner bought from a Hardware store that contains 16% W/W Sodium Hydroxide. So for me to mix a batch up that will compare to the commercially bought one do I need to add 12.8parts water? Based on

Or is my maths wrong?


Mike Warren:
I experimented with that about 18 years ago and never got as good results as the proper developer. There seemed to be too little difference in how it attacked the exposed vs unexposed areas. I concluded that for $2 a packet it wasn't worth stuffing around with. I'd mix up a litre and it would last in a sealed bottle for at least 6 months. Just don't mix used developer back in with unused.

Have a read of the 'developing' section of Mike's article


I used to make experiments with photosensitive laminate from Bungard (some people fabricate such laminate themselves with photosensitive spray).

I had some drain cleaner which according to the sticker was like 70-80% per weight NaOH. I found it extremly hard to mix correctly working solution. According to various manuals, general guideline is about 7g of pure NaOH per liter of water.

And ofc - 80% NaOH can burn you skin really badly - don;t ask how I know that :/

Your piping system can be very much neglected in many households. Like an appliance, pipes must be kept clean so they can function at optimum conditions. Intake pipes pose no problem because they carry only clean water. On the other hand, drain pipes and sewers can be as dirty as you can imagine.


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