because I'm reading prices will be going up, I'm thinking I might buy the muslin for my GFG now, instead of waiting until I'm at that point (I was waiting because I didn't want to have to store it or use it for something else). However, I don't know which is better, bleached or unbleached and what is the difference between the two?

Good question!! I have always wondered the same thing.

You might consider the difference between Premium Muslin vs. Regular Muslin. The thread count being the main difference, the Premium is finer, smoother, and presents a more sophisticated end product. Regular muslin works well with feedsacks (and reproduction prints), homespuns (and their new version called the 'wovens'), and 1930s prints. It is the color difference between bleached and unbleached; whether your color scheme works better with an offwhite or darker tone. Here's a description of first quality Roc-lon:
Superior Thread Count, Superior Finish
78x78 Thread Count
Weight: 3.4 oz.
Preshrunk

In contrast, "Premium" often has a thread count of 128 x 128.
Better to buy a bolt of each, eh? Oh, and by the way, there is DARK Tea-dyed; MEDIUM Tea-dyed; and some mfg. have created one called 'Antique' (??)

I think it depends on if you want white or off white. Depending on the muslin, I think the quality would be the same.

Within the same brand, the only difference would be the color. Bleached is white. Unbleached is off-white or natural colored.

If you have unbleached and you need white. Wash and use liquid bleach in the wash. Let the load soak then wash out.

This is good info, am printing this off. Thank you:)

a wealth of info here. thanks all.

I think it's safer to wait and buy the muslin when you are ready for it. Cotton prices are already at an all-time high; even if they go up further, it won't make that much difference in the total price. Plus, if you buy now you really need to buy extra to make sure you don't run short later. Whatever you buy now may not be exactly the same later if you need more of it.

Roc- Lon manufactures several different grades of muslin in both bleached and unbleached. Brand is not the only indicator as to the quality of muslin.