As to the archival properties of Echizen Washi papers the best answer is yes & no as it really depends on the particular pattern.
Overall the base stocks are archival but some of these papers have embellishments and inclusions that may not be archival. For the most part it would be safe to say that internally the base stocks of these papers are neutral pH but given the enhancements to the surface of some it may affect being totally archival. No different than putting acidic inks or chemicals onto a sheet of acid-free, neutral pH printmaking paper during a variety of printing processes.
We hope to have answered your question without being too confusing. If you need any additional information please do not hesitate to ask.
Overall the base stocks are archival but some of these papers have embellishments and inclusions that may not be archival. For the most part it would be safe to say that internally the base stocks of these papers are neutral pH but given the enhancements to the surface of some it may affect being totally archival. No different than putting acidic inks or chemicals onto a sheet of acid-free, neutral pH printmaking paper during a variety of printing processes.
We hope to have answered your question without being too confusing. If you need any additional information please do not hesitate to ask.