Draw Tite peeling from old lime mortar wall!

[jdpatten]

The house (My home) is 150 years old. The plastering was done with what's referred to as "lime mortar" which is slaked lime, sand, and cattle hair. It's had a century and a half to cure. I used Draw Tite on this wall and adjacent walls that are of well cured structo-lite. Having discovered Draw Tite while browsing this forum a few years ago, I used it along with Swing Prepcoat with great success on two other paper installations (Carter & Co) in this same house with great success. As a matter of fact the DT was very useful in reconsolidating the soft old mortar walls. So, I was quite surprised yesterday when the Draw Tite No Run that had been drying for about five hours seemed to remain soft. Naturally, I poked at it gently and when I scratched at a rough spot, the DT tented and peeled away. It came off in sheets in some areas. Today it still peels, though it's not quite as soft. Structo-lite treated walls are fine, as was expected. I thought DT would cure the sunburn syndrome, not cause it! I tried Gardz on a small area that had peeled. It went on thinner, dried well, and then peeled as well, though a bit less freely.

The questions are: How do I remove the stuff? There must be an easier way than picking over the whole wall (7.5 feet by 12 feet, other walls are Structo-lite).

What happened?

What do I do with the wall once the nasty stuff is off? I plan on more of that nice $ Carter & Co product.

[Bill Archibald]

Jeffrey,

You've described the situation well, but I am still somewhat confused.

The problem wall does not have the structo-lite over the horse hair plaster, right? (there seems to be disagreement as to whether horse or cattle hair was used - I've even heard swine and human hair were used and also hemp)

The D-T was applied to the old plaster?

Can I assume the problem wall (if it does not have the structo-lite on it) is what is typical for that era here in Mass. The surface is not a smooth hard white finish coat of plaster? It is somewhat rough, slightly pitted, and you can see the grains of sand ?

You said that you have found that D-T was "useful in reconsolidating the soft old mortar walls". Was the plaster on this problem wall soft and powdery?

Is this wall an outside wall or one that has been subjected to any water damage?

Usually, if plaster has become powdery, it needs to be removed and repaired. The old timers have said that a vinegar wash will sometimes help "reconstitute" effloresced plaster. I worked once for me on skim coat that was subjected to slight water damage. I would not rely on D-T to re-bond plaster that has turned to powder.

Can you offer more information?

If none of the above problems exist - no moisture, sound clean plaster - then I have no idea what happened.

[jdpatten]

OK. The old lime plaster is as you described - rough, pitted, sandy and one coat. When we first moved in almost forty years ago I worked on "reconsolidating" the old walls, reading what the NESPA had to offer. I concocted something that was similar to DT I think, involving Rohm & Haas's Romex AC-234 resin, Photo-Flo surfactant, GE anti foaming agent, water, and alcohol. It worked great - soaked right in, hardened right up, made the wall firm again. These walls seem to have deteriorated physically rather than chemically. The originally lean mix was no doubt bumped into pretty often. It's the hair - indeed cattle hair - that kept it all together until my potion treatment. No damp or mildew, no efflorescence, no powdering. I've recently been using DT for the purpose pretty successfully until now. This time the DT hardened on the other wall fine, but not on the old lime wall. The second day it's a bit harder, but there seems to be almost no penetration and little bond. Is it the gel in the no drip formulation? My main problem is how to get the stuff of without destroying the wall. ??

BTW, I've read other threads, and I'd like to clarify something. The hydrated or "soaked" lime that cements the old mortar plasters together actually takes several years to fully harden. It will be fairly firm after the first few weeks of drying, but will become calcium carbonate - virtually limestone - only after many months of absorbing carbon (dioxide) from the atmosphere. It actually gains mass in this slow process.

[Bill Archibald]

Not sure how to get it off. If it has gotten better, perhaps the best solution is to let it be for while and see it it changes.

Just an aside that prolly has no bearing on your problem. You said the old plaster was "deteriorated physically rather than chemically. The originally lean mix was no doubt bumped into pretty often."

I would think most of the keys had broken. How did you reattach to the lath ?

By a lean mix, I assume you are referring to a higher ratio of aggregate to lime, and not what happens when gypsum plaster has set too long before application. If so, many times the ratio of sand was too high in an effort to save a few pennies and the plaster does not hold up over time and abuse. I have that situation in my home. I removed those "dead" areas and re-plastered - with structo-lite as a base coat - yes I threw some HORSE hair in the mix. (BTW, how can one tell the difference between equine and bovine hair embedded in century old plaster? without DNA testing :devil:)

Obviously you have done some research as to the characteristics of lime plaster :thumbup: Did you give thoughts of repairing this plaster with a watery mix of lime - basically a white wash? The ability to repair lime plaster in this manner makes it a great material.

[Bill Archibald]

Jeffrey,

Another factor that should NOT be an issue since the plaster is so old is the pH of the wall. As you know, lime has a high pH, but it does level off with time - especially after 150 years :D. Is there ANY chance the wall's pH could be too high? Did you or is there any chance you can test for pH?

This is a shot in the dark, but just thought that base should be covered.

You didn't do anything TO the wall to raise its pH, did you?

BTW, want to see a REAL peeling sunburned skin syndrome?

http://billarchibald.com/misc/apeel.jpg

:roflmao:http://billarchibald.com/smilies/lol_above.gif

But the cause for this doesn't apply to you, unless you were REALLY testing products, mixtures, and techniques. BTW, I scraped this mess off with a wallpaper shaver and single edge razor blade.

[jdpatten]

Well, I guess this wall would be a good candidate the the lime wash idea - IF I can get the Drw Tt off.

Have you had success?

I only used the resin consolidating trick 'cause that's what the SPNEA did.
I just laid down a strip of masking tape to see if the situation's improved. I peeled it off along with a masking tape shaped strip of dry D T, leaving loose puckery edges behind. I don't think I want to trust that with my $ Carter & Company stuff.
Actually, I'm considering covering the wall with sticky-back "contact paper" and then peeling it off. What comes off will come off; the rest can stay. Have you never run into the need to remove D T or Gardz?

My first plastering job was restoring the 10 x 25 foot kitchen ceiling with a duplication of the old plaster using Ivory finish lime, local builder's sand, and, Tah daah - cattle hair from the Mohawk leather co in Nashua. It was tricky figuring how ti mix it all, but once done, made for a very nice piece of work. Good still after 30+ years. The cattle hair was a good match for the actual old stuff. Tell the truth, I don't know what horse body hair is like, but the horsehair used to stuff sofas is much too coarse.

[Bill Archibald]

I would try shaving it off with a blade. Something bothers me about sticky back something being applied and ripped of - maybe I've seen to many comedy skits with duct tape and body hair :roflmao:

Have I had much success with a lime wash ? Not much, but enough to impress me. I've usually just removed the dead stuff.

BTW, besides the internet plaster resources (and there are a lot of good ones) this is a good book. I borrowed it from my local Library:

http://ecx.images-amazon.com/images/I/41g0aKsaEZL._SS500_.jpg

Plastering: Skills (Paperback)
F. Van Den Branden (Author), Thomas L. Hartsell (Author)
Publisher: Amer Technical Pub (July 1, 1985)
ISBN-10: 0826906575
ISBN-13: 978-0826906571

amazon link is:

http://www.amazon.com/Plastering-F-Van-Den-Branden/dp/0826906575/ref=sr_1_45?ie=UTF8&s=books&qid=1257545892&sr=8-45

From what I can gather, hair of abundance was used. In the city, horses were abundant, in the country cattle or swine. Out where you are, it was dairy country back then - or even oxen. Here around the city, horses populated every barn. I also heard they would go up to Suffolk Downs where the race horses were. Ah, the tales passed down and now taken as fact :toast:

[jdpatten]

Wow, that's a really peely wall! Would that mine were so. Mine is a bit stretchy and comes off in smaller shreds.

I didn't test it, figuring on age. I do plan on a good vinegar wash once I get it clean. What do the Draw-Tite people say about pH?

Yes, lean meaning scant lime.

This wall has good keys, but last year I completed a ceiling reattachment project. The parlor ceiling is 14 x 16 feet. Sometime in the 30's furring strips had been nailed up to hang paper-board tiles. (You find the joists by bashing a series of nails through the perfectly fine plaster until you finally don't hit air on the other side, right?) Once I had all the stuff off I had a series of severe hammocks. Cattle hair held everything to the remaining intact keys. In some places the key failed because the lath was too closely spaced. The procedure: drill a pattern of 1/4 inch holes 6 inches or so apart coinciding with the lath. Vacuum out crud. insert garden sprayer with tip removed so that it only sprays laterally. After the lath and plaster have a good soak-in inject one trigger pull of clear acrylic flexible caulk in each hole. (Clear is softer than pigmented, allowing for better spread. Flexible to accommodate seasonal dimensional changes in the wood lath.) Apply polyethylene covered 1/4 inch plywood to the whole area and prop it in place with the removed furring strips arranged slightly flexed floor to ceiling - a more proper use for them. Next day remove plywood and plaster-patch the cleaned out holes. Repeat above until whole ceiling is done. Now that the ceiling is secure, wash off many layers of kalsomine. Once dry, apply DRAW-TITE! (It worked then!) Spackle, sand, and D T again. Paint.

Hey, you asked.

But I still have to remove the failed D T from the wall!

[slateberry51]

Oh dear, I wish I were the only person that ever had to deal with this problem. I never positively ID'd the peely white stuff on the walls in my kids bedrooms when we removed the wallpaper, but it looked just like the picture in this thread. We considered partial removal, but decided to laboriously take it all off. My painters used warm water and scrub sponges, and a lot of patience. it did not dissolve in the water; just kind of rolled up into gummy bits. I thought that the previous homeowner must have used an inappropriate wallpaper primer, but it may have just been the vagaries of a 120 year old lime mortar base that caused the primer to behave so badly.

Underneath was bare 120 year old plaster, in fairly good condition. We rolled on a coat of Farrow and Ball stabilising primer (which looks and behaves like watery elmer's glue). The painters loved it, said it was the best thing they ever saw for old plaster. After that we used Ben Moore aura paint, although it being a kid's room (read: many things taped to the wall and later pulled off), I wish I'd primed over the stabilising primer with something that had more tooth--the stabilising primer is quite smooth, and when the paint is subjected to the tape abuse, it sometimes comes off too.

I love the texture of Swing prep coat; had I known more at the time, I might even have considered adding a coat of that before I painted, even though it is sold as a wallaper, not a paint, primer. I guess what I'm saying is that the stabilising primer is great at stabilizing, but I'd call it more of a pre-primer, based on my experience.

Not sure if I've added anything the old pros don't already know, but perhaps some of my story is useful/relavant to your situation.

[jdpatten]

Thanks, slateberry. The farrow & Ball sounds like just the thing. I got this from their site just now:

"Availability: In 5 litre tins in white only. Dries clear. Available direct from the factory, Farrow & Ball Showrooms and selected stockists worldwide.

Description: A medium duty, solvent free, penetrating and stabilising sealer.

Formulation: An acrylic copolymer resin, with excellent alkali resistance and adhesion to masonry surfaces.

Usage: For use on interior and exterior masonry and plaster surfaces which are porous, chalky or lightly degraded but otherwise structurally sound. Provides a well-bound and durable base."

I'm wondering if any of the Professional Paperhangers have experience with this?? Does it compare with D-T or Gardz. Does Prep Coat adhere to the glossy surface?

So, slateberry, to get more specific please, what's a scrub sponge?


Bill, by shaving it with a blade, do you mean to use the razor as a mini push scraper. Thanks for the info about the book. My order is in.

[Bill Archibald]

Bill, by shaving it with a blade, do you mean to use the razor as a mini push scraper.

Yeah, I guess that would describe it well. You know how the guys get your auto inspection sticker off the windshield? Kinda like that but with a slicing motion too, like the deli guy does a nice thin slice of roast beast.

You are welcome about the book. It was written as a study guide for apprentice plasterers.

Slateberry, Fascinating what you say about the F&B stabilizer. Where did you get it? Waltham Wallpaper and Paint? If so, I may have to pick some up for future needs next time I'm in the neighborhood.

And there are many "appropriate" (or at least advertised as such) wallpaper prep coats that would exhibit the "Peeling Sunburn Skin Syndrome".

Romans R-35 is one of the more notorious ones, but that's because it was so widely used. I've had California Prep and Size do it for me, but only once. I think I did not let it dry long enough before hanging. (small bath. And then ice dams caused leak that necessitated a stripping and rehanging) And there was another white pigmented wallpaper prep that would do this if not dry well enough before hanging on top.

Swing has never done this.

[jdpatten]

Bill, I seem to recall a thread here a while ago that was doing a survey on changes in the Prep Coat formulation. I first used it about 35 years ago because that's what the local Fitchburg paper store carried. The store's long since gone and I used other preps until about 10 years ago. I made a grueling search and found some in NH. Same stuff, different label design: A small amount of flatting stuff that needed stirring and a light greenish tint. The Swing Prep Coat that I got in Waltham last week was quite different, with a lot more off-white stuff that needed a great deal of stirring and often. Still the same great performance? Do you know the up-shot of that survey? Stays even on glossy surfaces? I'm thinking here about slateberry's stabilising primer with P-C.

[Bill Archibald]

I can't remember the survey (senility, probably) but there was a batch of Prep Coat that seemed to settle rather quickly and when opened for the first time had quite a "sludge" on the bottom. Stirring it with any number of drill powered agitators mixed it quite well, but if left alone for a week or more, the solids would resettle - although not as bad.

I'm still using my stock pile of that batch. From what I understand, Alan, at Waltham Wallpaper and Paint, bought a large supply of that lot. I had the manager at Needham's S-W special 48 gallons from that lot. I dispersed many of those to the Boston Chapter. We've been dealing with it. As you say, same great performance.

I hear that Swing admitted there was that problem with that lot.

BTW, rumor has it that subsequent lots are better.

[Boston Hangman]

Apparently you must be a Mass resident to respond to this thread ;)

Jeffrey I apologize if this was already brought up ,but was the wall clean of paste or other residue before the DT went on? and if I'm not mistaken, the no run does not penetrate as well as the original DT.

As for removing it , if the razor scraper doesn't work for you, you could try cutting up a floor buffing pad from 3M. The official name is 3M -5100 red buffer pads aka 3M I.D. # 61-5000-3594-6. These are great and economical as one pad can be cut into pie shapes and yield approx 8-12 pieces. I used to get these at Town Paint , but they have gone the way of your store in Fitchburg:(

Now for really important question...have you ever eaten at the Moran Square Diner ...in my opinion a good take at least for breakfast!:thumbup:

Mark

[jdpatten]

I must say, Mark, the diner is a beautiful old "building" that I pass by most days. I do pass it by, though. I should stop in?

Do you suggest using the buffer pads dry? Maybe a little water or alcohol to soften and lubricate?
I still kind of like my idea of sticky back contact paper to "wax" the wall. The D-T still comes off with masking tape after 2 days of drying with no harm to the plaster surface.

Say, I bet there are all sorts of old plaster problems all over New England... maybe even beyond.

[jdpatten]

Oh, yeah, the walls were clean.

[Bill Archibald]

Say, I bet there are all sorts of old plaster problems all over New England... maybe even beyond.

Nope, we are God's chosen, blessed with Celts, Pats, Sox, Brooons, Revs, and plaster problems. :thumbup: No one else, just us !

BTW, Jeffrey, leave March 13 open on your calander. The Bershire Chapter of the NGPP is hosting their annual March Madness Workshop in West Springfield. Great educational opportunity for wallcovering knowledge and not a shabby networking venue also - yah we also get a little social too. ;)

Yes, non NGPP members are most welcomed, hell, they are ENCOURAGED to attend. Not a bad show for $20 - Continental breakfast and pizza lunch are included.

details will soon be posted on the NGPP website - www.ngpp.org

[Boston Hangman]

I must say, Mark, the diner is a beautiful old "building" that I pass by most days. I do pass it by, though. I should stop in?

Do you suggest using the buffer pads dry? Maybe a little water or alcohol to soften and lubricate?
I still kind of like my idea of sticky back contact paper to "wax" the wall. The D-T still comes off with masking tape after 2 days of drying with no harm to the plaster surface.

Say, I bet there are all sorts of old plaster problems all over New England... maybe even beyond.

Hey if the contact paper works then have at it. If you use the scrubbing pads it is best with hot water.

The diner is beautiful, but the pancakes are incredible. I stopped in on my way back from Jaffrey in September they had pumpkin pancakes on special. good stuff! I hope to stop for lunch on one of my trips when I'm out that way.

Do yourself a favor stop in and have a good breakfast before you tackle the removal of DT :lol:

[Jeff Evans]

Here's the Swing Prep Coat thread: http://www.ngpp.org/lounge/showthread.php?t=2032

I'm on 2 year old stock right now- at least- so I'm still dealing with the sludge problem. I just dump it in a 5 gallon bucket, take a Squirrel mixer to it and strain it back into the gallon buckets. After a couple days it settles and those need a good shaking again. It's still worth all that trouble, though.

[slateberry51]

Hello jbpatten, Bill,

Didn't realize you were so local! I just checked and I still have 2/3 can of F&B stabilising primer, would love to give it to either of you. I'm right around the corner from Waltham wallpaper and paint, so drop me a line next time you're in my neck of the woods. That bit about how it deals with alkali walls, I hadn't noticed before, but you're right, that's just the thing for these old lime mortar walls. In my case it was beginner's luck that I used it, but now I'm even more glad I did.

I ordered it from Johnson Paints, which has Waltham and Boston locations. They get all their F&B product from Canada, and it usually takes about a week to come in; kind of a pain, but the product is worth the wait. My kids are tough on walls and they still look new.

Prep coat definitely adheres to the stabilising primer. I just ran upstairs, put scotch tape on it, scratched hard with my fingernail, and pulled it off. Holding it up to the light I see no extra residue where I scratched. Not a scientific test, but a good sign. (Let's see, it's been two years since we put up the prep coat and I still haven't hung the wallpaper; maybe it's time to call a pro, ya think? :-) Calling the stabilising primer glossy may have been an overstatement, but it does not have tooth. Satin would best describe it. I've had no problems with paint adhesion where I followed the stabilising primer with traditional primer and then paint; it's just in the kids rooms where I went directly over the stabilising primer with BM aura that I've had any issues, and that was in a pretty abusive situation.

The scrub sponges we used were blue or green scotch brite type--and lots of them. hangman's suggestion to use the 3m product cut into wedges sounds very good and might be more cost-effective. My painters would take a 2 x 2 area, wet it down with very warm water, then wait a few minutes. They'd come back and scrub with the scotch brite pads, going over the whole area until it was done. They went through a lot of sponges as the peely stuff would gum up the sponges after a while. I think they used wide scrapers too. The test areas took 20 mins to do, and we figured 20 hours for a 14 x 16 x 9 room, but somehow it ended up taking about half the time, so we were glad we did it. It was like the Karate Kid though, wax on, wax off. Still, ten hours compared to years of wall problems--I think it was a good trade off. They may have had Dif in the warm water, but I can't recall. It might be worth a try.

I got my Swing prep coat at Nickerson Hills in Waltham, another great place. Is it just me or is the paint store community around here like family? I feel like I'm walking into Cheers every time I go to buy paint. I love Waltham.

Don't forget Wilson's diner; another beauty, and only 1 block east of Waltham wallpaper and paint.

It's been nice chatting with you pros, thanks for listening to me go on and on about my walls. I'm in an old Queen Anne and I love talking about any aspect of it. Also jd, my painters also live around the corner, if you want me to get in touch with them for any more details/anecdotes about their removal technique i'd be glad to.

Best,
Alexandra

[Bill Archibald]

Yes Alexandra, time to hire a pro :thumbup:

I'd make a shameless promotion for myself here, but I'm not that type :D especially when the link to my web page is in my sig line :devil:

Speaking of Boston Hangman's suggestion for the floor buffing pad, if you need something coarser AND with a handle try a grill scrub usually found at the Despot or Lowes.

http://images.orgill.com/200x200/8997801.jpg

AND when the pad wears down, you can hot glue a piece of the floor buff pad to the handle. Those large floor pads are VERY cost effective ! I find the handle saves the fingers and allows one to apply more pressure when needed.

Thanks for the info about Nickerson & Hills. As much as I love giving Waltham Wallpaper business, N&H is easier to access from 128. As you know, that additional 3/4 mile to WW&P is a real bear.

Also, I had forgotten Johnson now has a retail outlet in Waltham (and the contractor store in Woburn). I know they are a great supplier of F&B paints. Thanks for THAT reminder.


-Bill

[jdpatten]

Well thanks guys, for all the suggestions. Whew. Let's see, there was razors and buffing pads and lime washes and books and pH's and prep coat surveys and D-T alternatives and alternatives to avoid and pad handles and...and... a diner for breakfast!! Yes, I shall attend the March Madness, thanks. And, I'll let you know how this #*%# wall works out

[Buff1]

BTW, Jeffrey, leave March 13 open on your calander. The Bershire Chapter of the NGPP is hosting their annual March Madness Workshop in West Springfield. Great educational opportunity for wallcovering knowledge and not a shabby networking venue also - yah we also get a little social too. ;)

Yes, non NGPP members are most welcomed, hell, they are ENCOURAGED to attend. Not a bad show for $20 - Continental breakfast and pizza lunch are included.

details will soon be posted on the NGPP website - www.ngpp.org

Check with Silent Slim...I think the MMVII is scheduled for Saturday, March 20th.

[Boston Hangman]

Yes Alexandra, time to hire a pro :thumbup:



Speaking of Boston Hangman's suggestion for the floor buffing pad, if you need something coarser AND with a handle try a grill scrub usually found at the Despot or Lowes.

http://images.orgill.com/200x200/8997801.jpg

AND when the pad wears down, you can hot glue a piece of the floor buff pad to the handle. Those large floor pads are VERY cost effective ! I find the handle saves the fingers and allows one to apply more pressure when needed.

-Bill

The 3M round pads do come in coarser versions than the red . I haven't found it necessary to use anything coarser , but stripping the DT might be the exception.

Buffy is correct MM is 3/20:tiphat:

Mark

p.s. I'll try to make it to Wilson's :thumbup:

[Bill Archibald]

Sorry,

March 20 is the updated date for the March Madness Workshop. Brain fade.

And the courser pads ARE too course for many removal applications, but Mark read my mind correctly - they may be best for DT removal.

[jdpatten]

So far, no good. I got the red disk and hot water and went to work. Starting at an open edge where I'd peeled it away with masking tape, the process seemed to smooth down the loose edges and just polishied the tough surface. The coarser mesh does eventually abrade away the D-T, but it's hard to tell where, because it dulls the surface, making it look like bare plaster. Looking closely after a wipe & dry,however, you can see that the surface of the plaster has been abraded away too, exposing the lean sand mix. So I'm off to the hardware store to buy up their really really wide masking tape. It still comes off pretty cleanly with masking tape. My idea of "contact paper" wouldn't fly 'cause it's not as sticky as it used to be. Too many complaints of paint being ripped off shelves, I guess. Where are they when you need 'em?

[slateberry51]

Sorry to read that my removal technique did not work for you. Maybe my gummy gunk was something else after all. Whatever it was, I'm glad it's gone, and hope yours is gone soon too!

[Bill Archibald]

So far, no good.

Jeffrey,

How about calling Scotch Paint out in Calif and see if they know of a solvent or other solution.

according to their website:
http://www.scotchpaint.com/

the phone number is
1-800-404-2878

They are a small company, and are known to be very helpful.

[jdpatten]

Thanks, Alexandra. I just now pulled the last of the duct tape off the wall. It worked. Turns out masking tape wasn't quite sticky enough. The tape removed 99% of the stuff. Now I'll use Mark's 3M red pad and hot water to clean off the few loose edges. It's interesting, there are a few areas of thin gypsum plaster patch that the D-T worked so well on that the tape pulled areas of them right off the wall. I figure a good strong wash with a salad dressing... uh, I mean vinegar rinse and dry, and I'll be able to apply Draw-Tite again - to a VERY small test area. It's worked so well before, I figure it's worth a second chance.

Bill, I know that some Rohm & Haas acrylics use acetone and/or xylene as solvents. Not certain that's something I'd want to mess with. I'll certainly talk to Scotch about the whole thing before covering the whole wall again.

[Chris Murphy]

You don't just "wash" the surface of hot plaster to knock down the pH; you keep spraying it on until the wall has absorbed all it can. The plaster will absorb an incredible amount of the vinegar (acetic acid)/water mix. When the wall has enough, it will begin to run off; the wall will have a sheen from all the moisture. Then, of course, you have to wait for the wall to dry. Being the heating season, that shouldn't take long but I'd give it a few days anyways.

You should look into a pH pencil from Micro Essentials Lab. They're the only thing I know of to accurately test the pH of a wall.

[jdpatten]

Right, Chris. Thanks. I've got my trusty three gallon garden sprayer ready to go. What I've experienced on my other walls is that the lean old lime/sand stuff is fairly reluctant to get wet, even though bare and clean, so I keep at it for a couple of days. Wetting the base like this is necessary for Structo-Lite or any sort of gauging plaster/ lime repairs. I discovered that once the wall or ceiling has been thoroughly wet and then allowed to not quite completely dry, it's much easier to wet again. I've done this a lot and, after an appropriate drying period, never had any trouble with sealing with my own acrylic emulsion recipe, Gardz, or Draw-Tite - until now. (All this is in the one house, my home, where all the plastering is the same.) The best thing would be to find out what's going on, but I'm sore tempted to just proceed with a small test area (way behind as it is) rather than wait for the $30 one-time pen. I dunno, maybe I'll get one anyway!?

[Chris Murphy]

You don't need the pencil (not the same as pH pens) for the walls you're working on; you've already found a way to see if that plaster is hot. (!)
But for future work, you could try it.
And just because all the plaster is in the same house doesn't make it all the same. Something is obviously different about these walls, and it could have been the guy who was mixing the ingredients- all you can do now is avoid future problems either by testing them with a pH pencil, or giving them the vinegar wash.