Hi Jukka,
hardening fixers may contain acid components or not. Acid components have absolutely nothing to do with hardening capabilities. Normal fixers are acid, whether "rapid" or not. Only fixing baths for C41-processes are neutral and require the use of an acid stop bath.
A300 is a fixing agent based upon sodium thiosulfate, thus not a modern "rapid fixer". It consists of sodium thiosulfate and sodium sulfite for conservation purpose. Nothing else added. A cheap, simple, traditional recipe.
Hardening fixers have some formaldehyde salts added and are based on ammonium thiosulphate. Most commercial fixers (except noted) are non-hardening fixers. Even rapid fixers are non-hardening as both paper and film are very much pre-hardened today (except Adox/Efke films).
Sorry for my rotten english. I'm much better in chemistry than in english:-)
Best regards,
Franz
hardening fixers may contain acid components or not. Acid components have absolutely nothing to do with hardening capabilities. Normal fixers are acid, whether "rapid" or not. Only fixing baths for C41-processes are neutral and require the use of an acid stop bath.
A300 is a fixing agent based upon sodium thiosulfate, thus not a modern "rapid fixer". It consists of sodium thiosulfate and sodium sulfite for conservation purpose. Nothing else added. A cheap, simple, traditional recipe.
Hardening fixers have some formaldehyde salts added and are based on ammonium thiosulphate. Most commercial fixers (except noted) are non-hardening fixers. Even rapid fixers are non-hardening as both paper and film are very much pre-hardened today (except Adox/Efke films).
Sorry for my rotten english. I'm much better in chemistry than in english:-)
Best regards,
Franz
