Good evening

I recently bought a nice Graflex B-stationary 3 1/4x4 1/4, in good conditions except for the curtain that was detached and in bad, dry, cracked conditions.

I removed it and I cleaned the two spools in order to accept the new one I'm making.

Does anyone know about pre-tensioning of the lower spools' spiral spring? I need to reach an acceptable tension before refine it with the aid of a photocell instrument to measure the correct shutter speed.

Curtain at full closed initial tension of 6 turns will work with an excellent spring. 8 to 12 turns is normal for most cameras. 16 or more turns there is a problem.
Curtain must close fully from O on tension 1 with the camera in any position.
Curtain must wind to smallest aperture/slot with the tension at 6.
Increasing the initial turns will have little effect on shutter speeds with a weak spring or worn roller bushings.

Thanks.
At this time, I bought a curtain fabric in Japan, but I found it too "modern" for my Graflex, does anyone know what type of fabric is in the curtain and what paint they used in 1920s?

Rubberized Silk or Cotton. Player Piano bellows cloth .008 inch thick is as close to factory original that is available today.

Thank you