"paint-like" spots on rafters

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Hello, first posting to Usenet so hope all goes well...

I just got up the nerve to inspect my attic (unfinished, just beams and stuff) ... I noticed these light, tan-colored splotches of color on the rafters that LOOK kind of like random paintbrush strokes, dispersed among many of the rafters. Some splotches are big, some small. Some rafters don't have them at all.

I've prodded the area with a screwdriver and the wood seems sturdy enough. When I rub one of the spots with a finger it feels kid of powdery. It's a foreign (to the wood) substance of some kind, but what?

There is also -- noticeable if you stare at them for a moment -- a faint "sparkle" to the rafters in general, as if someone coated them with, well, faint sparkles. (And, no, I don't take drugs ;)

The roof has a fan cut into it, and all seems dry, no signs of water damage. When I shut off all the lights I don't detect any pinhole light getting in or anything. Roof looks okay from the outside (no bad shingles, etc.) The house was built in 1958.

Any idea what these spots might represent? I'm pretty much a complete novice, as you can tell. :) Should I worry or be happy or just .. be?

Thanks for any help/ideas anyone could offer.

[Roger]

I noticed these light, tan-colored splotches of color

Powdery texture suggests mold or mildew spores. The wood underneath is solid, so it is not dryrot. If it is mold (may take an expert to tell), you should look at how well air is moving through the attic.. Check to see you have lots of unobstructed eaves vent holes to allow air to be drawn up through your ridge vents. Ideally, you want enough ridge and eaves or gable vents to create good circulation throughout the space. Once the attic is well ventilated, you can put on a breathing mask and spray the mold with bleach to kill it. Sometimes tiny balls of pitch that ooze from poorly seasoned wood will concentrate light and look sparkly. If you try to rub the sparkles off, and they stay, it might well be dried pitch. Nothing to worry about. Could also be some crystalline substance (what?).

[Joseph Meehan]

Bird crap?

[E Gregory]

If the "paintbrush strokes" are about 1 inch wide or less and in a verticle orientation most likely there have been mud dobber nests there in the past. Eileen

[Jeff Cochran]

Sap laking out over the years as the wood dries further, then crystalizing. Common and harmless.

Jeff

[Heathcliff Bambino]

The sparkly stuff is little beads of sap that have oozed out of the wood and hardened. Perfectly normal. It'll be amber in just a few million more years.

As for the splotches, I would guess most likely it is old wasp nests, as another poster suggested, or possibly mud that got on the lumber when the house was being built. Doesn't sound like anything to worry about. If you go up there in summer you might want to look out for wasps.