The Gramercy mix: 1/3 409, 1/3 ammonia, 1/3 water.Like

I am scared by random people writing this and that with compressed air.We learned in typewriter school in the navy.1.remove rubber bumpers platen and feed rolls.2. Mix 1to 1 superagetine and mineral spirits. Stoddard solvent also works.3. Soak overnight.4. Drain and rinse with fresh solvent.5 air dry or bake @95°F.6 .cool and manually re oilNow a day oil only with synthetic 0 weight oil.7 .check and brush typefaces.8. Clean platten.Reinstall and type test, align typefaces. Only permanent align is peening typebars. This is the way I maintained 200 typewriters on an aircraft carrier.This what worked for me.Spring scale at .75 Lbs. For tape tension.Adjust the rail clamps and clean under if required. Carrage should slide with 3 oz or lessLike

This has been an ongoing "philosophers stone" in the repair community for a long time. Hard platens are the result of the rubber losing its moisture, there's virtually no way to fix that long term. Brake fluid, rubber renew, even the wintergreen oil trick only temporarily soften platens/feeds. They will absolutely go back to their former state after a time. (1-2 months) You can sand the exterior and clean with organic solvents to restore grip and improve the original platen, but recovery is really the only long term fix. *There's a ton of back and forth about the sanding method, particularly from the old timers being salty about it. But I have seen HUNDREDS of old platens in machines that have absolutely been sanded by repair folks back in the day, so there's definitely value in the process.