What is this black caulk-like stuff ?

[Willa]

I started to remove the paint around the front door, as the texture was very pimply - almost like shellac or varnish had been applied that sort of beaded on the surface, then was painted over. The only way to fix this bad texture was to heat gun it off. There are a million holes to fill from the awkward weatherstripping. The door couldn't fit correctly due to a false threshold that had been nailed down that was just a little off - due to a chunk of old carpet and a nail below that. Once those were gone, and the dumb threshold over a threshold were gone the door fit much better in the jamb.

I have always wondered about the caulk-like stuff that is around the doors and windows here. Most of it is cracked, though remains solidly in place. While I was heat stripping some of this was uncovered, and revealed itself to be a black goo that was very responsive to heat.

Does anyone know what this stuff is, and what I should do with it ? I am starting to prep stuff for painting. Do I warm it up with the heatgun and smear it more solidly into place or dig it out to replace with fresh caulk ?

Pic shows the heavy caulking like stuff that is painted over and cracked and pulling away from the brick:

_DSC0001.JPG (663.29 KiB) Viewed 455 times

Black goo revealed under paint:

_DSC0003.JPG (718.19 KiB) Viewed 455 times

[GibsonGM]

Looks like it could be roofing tar. "Back in the day" they'd use anything at hand to seal joints...there wasn't any caulking back then, not like we have today. Often they'd use glazing compound, too.

You're wearing a VOC-rated respirator when you heat this stuff (and the paint), right?

[Seabornman]

Could be a butyl based caulking, like is used to seal gutters. It never completely sets.

[Olson185]

My contribution falls somewhere between GibsonGM and Seabornman but differs only in degree.

I had to look up "butyl" because I know artificial rubber was developed in the late 1930's - early 1940's, because the sources of rubber were limited because of events leading to WWII, but wasn't sure if this was "butyl" or not...it was.

I think roofing tar would retain its odour; especially if re-heated. I'm not sure what butyl would smell like heated but would suspect it would soften less readily than roofing tar. If you'd like to ask me about that nasty black linoleum adhesive...I know much more about that, lol.

According to TCP Group, ExxonMobile, and a couple general info. PDFs: There are different "butyls" so no one characteristic may exist with all types. Today's butyl-based caulkings are different than what was made in previous decades but today's (since around 1980) caulks are fairly similar.

Butyl based caulks will completely set. Some take a long time to do so. All old butyl-based caulks will shrink during setting. And, for this reason, I would be inclined to remove what I easily could and fill-in with something new.

[GibsonGM]

Good call, Olsen. Yup, it could be that. Even more reason to wear a respirator if you're heating it up

[Willa]

I'm working outside at an arms length distance so I am not wearing a respirator. Glasses make finding a well fitting respirator that doesn't fog them up or make them sit too high (progressive lenses) a real challenge, too.

I haven't noticed a particular odor when I've softened this stuff up - like not ashphalty - like roofing tar - or anything else. I assume whatever this goo is, is late 1800's stuff as the doors and windows have not been replaced, and maintenance here has been very frugal/minimum. I was expecting something resinous maybe ? I guess I'll have to look through "Lee's Priceless Recipes" to see if there is any corresponding info ?

I'm light with the heat gun as I don't want to superheat anything that might be flammable, and I especially do not want to crack the pressed glass in the transom.

[GibsonGM]

Just a gentle prod, Willa We're all taking some form of hit every time we work. Heat gun under 1100F won't vaporize lead, but you still generate very fine dust that you inhale...and who knows what comes out of butyl, tar, or whatever it is? I know what you mean; respirators are nearly impossible to work in.

A paper type N100 rated for lead is a really good thing to keep around as it'll block most all dust if used correctly. I try to wear it, but sometimes....lol Won't stop fumes, tho.

[Mick_VT]

My Home Despot purchased fume safe respirator works fine with my progressive lenses

[Willa]

I tried to wear a basic particulate mask when sanding plaster this winter and it fogged up and I couldn't see a thing. A long, long time ago I had a respirator with canisters for different chemicals, but the fit was so bad it gave me a painful roman nose for days afterwards.

Head size, facial proportions, glasses style and size make the respirators fit about as well as one size fits all pantyhose. My prescription is pretty intense so I have to tilt my head up for work that is closer than 14".

If I did this for a living in close quarters I would be more concerned. My lifetime exposure to mystery black goo will be minimal= basic vision is prioritized.

Lee's Priceless recipes (c.1895) suggests the goo might be:

- Roofing Cement, pg 177 - a mixture of common pitch and gutta percha (is meant to be smoothed over with a hot iron tool)
- Universal Cement, pg 186 -isinglass, plus acetic acid. Liquid when heated, solid at room temperature
- Roofing Cement, pg 191 - red oxide of iron, boiled linseed oil, japan dryer, Roman water and venetian red
- Artificial Rubber, pg 315 - glue plus tungstate of soda and hydrochloric acid. Very responsive and pliable when reheated

or none of the above ?

[GibsonGM]

I'm in the same camp; I have 20/500 vision. No glasses, I can't identify an object 2 feet away Often, the respirator hangs around my neck rather than being on my face Esp. when it's 80 out and I'm 35 feet up on a ladder. I'm no Safety Stanley (oh, I've pickled myself for sure - gotta have my lead level tested at the end of the season)...informed self-abuse is one's basic right, IMO. No different than smoking. I only put that stuff out there from time to time because it seems that many really DON'T know what they're inhaling or what it can do to you, and doesn't require much time to take a dose (and to bring it into the house for the rest of the family to have some, too)...I can tell by some of the pics, lol. If smoking a butt or removing asbestos pipe insulation doesn't make one recoil in horror, then by all means, proceed...I'm not picking on YOU, Willa. Most all of us do the same things - sanding sashes and so on. I don't exclude myself. It's all good.

I'm with Olsen, I think it's a caulk of some type, or a tar/rubber, perhaps the 1st or last in your list.