Filter for denoising of an old document scan

Question

I hope this is the right forum to ask this.
I've got some old documents (part of a drawing) that I want to scan, but the original documents are quite old and the color has degraded (although the paper itself is in relatively good shape). See examples (fairly readable, and really difficult to make out):

What I would like to know is :

what type of filters (preferably available in GIMP) would you explore to clean up this type of noise. My main aim is to make the text readable.
Get at least the name of this type of noise in the documents (english is not my native language), so I can research it further myself online.

I suspect there are many steps that need to be followed before you can process this, so I would appreciate it you could outline a possible algorithm, (e.g. 1. convert to grayscale, 2. threshold etc)

Abdul N Quraishi · Answer

The quickest way I have found to do this is via Luminosity Masks.

First REMOVE COLOUR from the image.

INCREASE BLACKS

SPOT HEAL dark areas of image not Required.

Create a CURVE Adjustment Layer

Select COLOUR RANGE

Adjust the curve to fade away the colour range.

Make multiple passes with New Curve Adjusments for each new Tone.

Do this until you're left with just the dark Tones.

Create a SOLID WHITE LAYER

Select COLOUR RANGE and colour pick the chart

Create a NEW Layer with this Selection and drag it over the White Layer

Finally, just do spot healing to tidy up.

The process took me just under 5 minutes and below is what I am left with.
Please don't forget, I have just rushed through it and with more time and effort, you should be able to get a better result

Filter for denoising of an old document scan

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