Thanks to a friend, I have found it... and it changes my life.
Imagine being able to spread a butterfly just 4 hours after taking it from its enveloppe, even a difficult butterfly to spread like an Agrias or an Hesperidae.
Here it is : the "ammonia method".
For classic butterflies (Delias, Colias...).
- use a syringe to inject one or two drops of ammonia into the thorax between the legs, at the wings level. (see photo)

- if you have injected too much ammonia, absorb the excess by gently pressing the specimen between 2 sheets of toilet paper.
- place the specimen on a sheet of toilet paper in a classic relaxer for 4 hours (toilet paper will absorb ammonia if you injected too much).
- after 4 hours, you can spread it
For tough butterflies like Agrias.
Same method but add an ammonia injection between the eye (see photo)

This is the result, that picture has been taken 4 hours later the first 2 pictures

This method is really a game changer. You can spread an Agrias in 4 hours instead of several days. No mold risk. No more broken antennae. No more holes in wings because you force too much on them and so on. No greased wings (which happen with hot water on Agrias).
It is very practical, you inject in the morning and spread after lunch.
Just try it and let me know. Use pure ammonia that you find in every supermarkets.
One last tip :
- An open bottle of ammonia stinks. Fill your syringe to the maximum so you can prepare a dozen specimens without having to re-open the bottle.
