Jason, a robust formula is one that does not need Ammonia or other "crutches" to make it work. As Ian says, using chemistry to solve a mechanical problem is not right for his case.

I'll give another. The Axo type emulsion that is in my book works well with no pepper grain, and you can make it at 100 g - 3000 g scales with no problems as long as you supply correct mixing. If you go over 1 L for example, you have to use a mechanical stirrer and the magnetic mixer both to get proper mixing. Otherwise, you risk burning the gelatin on the bottom, bad mixing at the top and pepper grain. Deviation from the Azo type formula will cause problems.

In the case of Mark Osterman's plate emulsion, we have collectively made it over and over with no pepper grain and no Ammonium salts. It works perfectly as written. It is a robust formula. Deviation from the written formula will cause problems.

These are robust formulas achieved by lots of experimentation.

The Kodabromide / Brovira type formula in my book is robust.

Now, take all of these formulas and consider this, when a significant deviation occurs, pepper grain will appear. So, lets look at a poor formula for you to compare with. Make the Azo type emulsion with 1/2 of the amount of gelatin specified. You get just about the same results but with load of pepper grain. Or, take the Kodabromide / Brovira type formula and move 1/2 of the water from the Silver Nitrate to the Gelatin side and then make the emulsion. It is totally unusable due to pepper grain and aggregate. These two emulsions have been made stable without resorting to a chemical "trick".

I hope these examples from my experience help.

PE