Advice needed on cleaning up old beams

[MikeG]

Here's some of the carpenter's marks, and other points of interest.

In these, you can not only see the carpenters number for the joint, but you can also see the setting out marks for the mortise. You can also see that the brick inserted into the mortise and then plastered into place, 300 years ago (the timbers are 700+ years old) is untouched by the cleaning process. When this was painted with, ultimately, a thick shiny black gloss paint, there was no sign even of the mortise, let alone the other detail:

Setting out lines of uncertain use:

Here is some obvious sap wood, wormy and friable in places:

 

[pineapple]

Wow I need to have a careful look through all of this now that I'm back on line after a few computer problems.......
Yes the kitchen is yet another job. Not quite visible in the pic are the horrible kitchen units down one side. I am going to get rid of the wall units and just replace the floor units. Maybe not even that. I want it to look as unfitted as possible but I still need a sink unit of sorts plus storage and work surface and it's more difficult than it sounds.
So much to do...
Thanks all.

 

[Toby Newell]

looks good Mike.

pm sent to address some of your points, not beneficial to anyone here. If you have the name of the company that did the work then feel free to pm me.

 

[88v8]

Whichever method is used - and there's also plastic media blasting - the result and the damage if any, will depend on the diligence of the operator.

Dust-wise, with sanding at least the dust can be collected to a degree as one progresses, but I suspect that blasting of any sort is ill suited to an occupied house.

Ivor

 

[MikeG]

The dust produced by ice blasting is only the paint and other stuff removed from the timber being cleaned. The medium itself is a gas, and just drifts out through the windows.

 

[Toby Newell]

Whichever method is used - and there's also plastic media blasting - the result and the damage if any, will depend on the diligence of the operator.

My thoughts exactly. Ice temperature, pressure, material flow, distance from substrate, all variables presumably.

And Mike, sorry old chap I did send a pm but I think it's possible gas doesn't just hit the surface. In fact it may be factually inaccurate to say that. Just sayin. It's easy to check. Factually inaccurate is a fact, that is not accurate. It has nothing to do with the vernacular avoidance of calling people of power liars. Trump isn't factually inaccurate, he is a liar. You are not a liar (that I know of) but your facts, in this instance, are inaccurate. Instead of misreading, misunderstanding and taking things personally it may have been more fruitful for you to check your facts. In that instance you would of not only learnt something new but also avoided any offence. And I would not have needed to write this, so future browsers of these forums are furnished with the most helpful and accurate information possible.

Small solid pellets of carbon dioxide at < -78 degrees celsius with a density over 150% that of water ice get jet blasted at supersonic speeds towards the coated substrate. At the surface the pellets (travelling in excess of 750 mph) meet the coating. The impact energy forces the pellet apart in a mini explosion. As the pellet, still solid CO2, breaks apart it is able to heat very rapidly and sublimate into gaseous CO2. (Carbon Dioxide is relatively rare in that it turns straight from a solid into a gas without going through a liquid phase at atmospheric pressure) As the micro fine fragments of solid CO2 are in proximity to the surface they almost instantaneously absorb the energy required to form a gas (in the form of heat) from the coating on the surface, thus the surface coating is chilled to many tens of degrees below zero. This effect is very localised, ie only the top few mm are cooled in this way, creating a sharp temperature differential and consequent differential thermal contraction, it is these forces that help detach the coating from the substrate. Ductile materials (like bitumen and oil paint) deform elastically (returns to original dimensions after force is removed) at low force and at higher forces plastically (deformation remains after force is removed) when cooled below their 'brittle-ductile transition temperature' a material is too ordered and stable and doesn't have the 'wiggle room' to allow the faults in the material to move in order to deform, instead the force builds until it reaches a critical value and the material catastrophically fails, this is called brittle fracture.

It's very simple. You will need two curly wurly's. Put one curly wurly in the freezer for a few hours, put the other one in a warm room near a window. Try and snap both. There you go.

So CO2 blasting works by cooling the coating so it becomes brittle, then this brittle coating is broken apart and flung from the surface by the kinetic energy from the exploding pellets as the solid CO2 expands at explosive speeds into a gas.

I suspect size of pellets the pressure and material flow rate can make a big difference as will operator skill and experience. Still messy and still potentially damaging due to the forces involved as I have experienced, works very well on strong, dense substrates coated with softer ductile coatings like oil, grease, rubber, mastic, oleo resinous coatings etc. I respect Mike's opinion that it's totally spiffing, it certainly seems like he got excellent results and he is happy with it, but how the process works isn't an opinion, it's a fact. The results really do look good, so it would be nice for Mike to let people know the company if they asked. I would be very interested to see it in action. For example, this took me a hard week to strip as some plum had put a modern finish over the shellac. If a CO2 bod could do that in half a day, that would of been much preferable, stripping it carefully was not pleasant.



We won't mention the carbon footprint. Maybe walk for a couple of weeks to compensate.

(Quote from commercial dry ice blasting site)

Soft dry ice pellets are accelerated to supersonic speeds and then directed at a surface that needs cleaning. As the pellets impact the surface, small explosions occur. These mini-explosions lift the undesirable material off the underlying substrate.

PS. Please note excellent marketing. 'Soft' here means 1.5 times as hard as water ice. I suspect if you were blasted with harder than ice pellets at faster than the speed of sound the word 'soft' may be a stretchy adjective. Soft means close to sublimation temperature, most materials get slightly harder and denser as they get colder. So soft is relative in this context meaning not as 100% as hard as it possibly could be. Or compared to harder things, like plastic, or sand.

 

[MikeG]

You'll get no response from me until you apologise and admit your error in calling me a contractor, and for the accusation that I was marketing. In light of your insistence that I check my facts before responding, that is deliciously ironic.


Old chap.

 

[Toby Newell]

Again you misunderstand. Your words indicated you were someone, like a contractor, who has multiple experiences of the system and who is an advocate of it, that's all and that your enthusiasm should be balanced with alternative experiences. I also said it sounded like marketing as your words implied it was better than other systems. I am not accusing you of being anything, other than maybe slightly over inflating the superiority of the method. It really does seem in your case to have worked very well. I don't see the conflict here of me acknowledging that the technique appears to have worked well in your pictures whilst cautioning that it may not always be the safest method. I would never imply that only one method fits all circumstances.

I don't know how I would of checked if you were a contractor, whereas you can check the facts of how the process works in two minutes.

Again, please don't take offence I am not calling you a contractor or accusing you of lying just of giving out erroneous facts and perhaps in the process a slightly skewed view of dry ice blasting which can obviously be gentle enough on some projects but damaging on others, depending on the timber and presumably the particular company and operatives employed. Your experiences have been good, mine bad, I think that means that people should be cautious, that is what I am advocating. I do not need a reply, just to say my intention is give people as many facts as possible so they can make informed decisions.

Look at the positive, it is possible that you have found a company that has developed a gentle enough technique for wood, remember, this technique is used 99.9% in industry and has only relatively recently in the last decade or two moved into the architectural restoration sphere so operating procedures obviously would of needed to have been tweaked for operators who were almost exclusively used to operating the machinery on metal, ceramics and plastics. This could be the first 'blasting' technique that actually works, at least on beams. Which could prove very helpful to readers of these forum posts.

I don't really understand people's dismay at being wrong, I think I learnt most of the important things in my life and profession by being wrong. Being wrong is extremely good because it means you have the opportunity to expand your knowledge. I don't really know many clever people who are never wrong.

 

[MikeG]

We won't be interacting any more Toby. I find your attitude rude, self-aggrandising and offensive. Your inability to understand that you are in fact the person who has something to learn whilst pontificating at me is really laughable.

To anybody who wants to understand the process of cleaning old timber with dry ice, please remember that Toby has never ever seen the results of such work. Coming next........everything there is to know about the Kafue National park, by Toby Newel, who has never set foot in Zambia.

Ta-ta.

 

[a twig]

"You should have heard what he had to say about your pet hamster!"

"I wouldn't stand for that"

"Oooh, sock it to him!"

*grabs another bucket of popcorn*

 

[pineapple]

Hi folks
Just a quick update. The guy came round to do a test strip and spent nearly an hour doing a small area - resulting in a lightly varnished bit of beam as opposed to a heavily varnished bit of beam. It does look better, being lighter with some visible grain, but he was expecting to remove more finish. He expressed surprise at how tough the varnish was. He starting off at 60 grit and then changed to 40. Even that has left a smooth polished finish, because it has just spread the remaining varnish around. :roll: I was surprised at how lightweight his kit was and he says he would probably need to try a heavier duty one. At least, having seen what he can achieve in an hour, I am better able to work out what it would cost. Probably not much change out of £1,000
Unfortunately I don't think he is the craftsman I was hoping for. I've had a bad split repaired with a resin formulation. He was expressing amazement at how hard it was and was asking if I could find out what they used. In fact I got the impression that he hadn't seen anything like it - not reassuring.
I can do the sanding myself a bit at a time if it is just about taking off the dark outer varnish layer. In fact this retired female just had a go herself and achieved quicker results with her domestic Bosch sander. I was just hoping for someone with better kit and more actual repair skills (for some of the mankier bits). But he was rather too fond of saying they add character. Well only up to a point....
If I do go ahead with this, is there an alternative to plasterboard then plastering between the beams? A decorator friend has said I could simply hardboard between the beams then paint or stick up some insulated plasterboard and paint direct on that.

Still debating going with distemper for the entire ceiling....

 

[Toby Newell]

@ pineapple.

Probably easier not to strip. Your guy obviously lacks experience, let's face it, not many people strip beams. I have the best sanders you can buy and best abrasives but the difference would be relatively little if you don't scrape first. If you buy a tungsten carbide scraper and a few blades then try removing as much material as possible as this will reduce the abrasive melting the coating and clogging up, after that using a Festool ETS EC150 5mm orbit or an Rotex RO90 with P40 grit or P60 grit will smooth the surface without removing hardly any patination, just check for any makers or warding marks and work carefully around these areas if you want to preserve them. Mankier bits can be cleaned with a selection of sharp pointy objects (be creative) and by wrapping abrasives around similar or small sticks. The idea is to do as little sanding as possible. This is well within your capabilities but leave yourself several weeks and do a little at a time as the work is very hard, if you have any sort of tendonitis or joint problems it's maybe not a good idea as you will need to apply considerable force (ie near maximal or maximal effort) to scrape the surface without digging in to the wood. Unless you like waste and have deep pockets chemical removal or scraping of the bulk of the finish, especially if oil bound or bituminous is a prerequisite to all sanding processes and also means you can actually start off with a finer abrasive (P60 or P80 cf. P40) which will remove less timber and leave fewer marks.

You can use two part cyanoacrylate (superglue but with hardener spray) adhesive, I find Mitre bond to be the best (I have used a couple of dozen bottles or so from many different manufacturers) very handy for repairing loose bits and to stabilise cracks. I fill very little but use a two part polyester resin like Ronseal high performance wood filler which is one of the only products that actually does do what it says on the tin. I self colour the filler with universal stainers (you can make up several shades) before you add the hardener, it gives a better effect than colouring the filler afterwards.

@ Mike. Probably a good idea. I would of thought my apology was implicit. I will let others judge who was imparting scientific facts and who was not. There is a reason no blasting process is used by professional restorers for delicate work and cost isn't it as I said as any blasting is likely to be an order of magnitude quicker and therefore cheaper. Myself and I am sure many others on this forum would be genuinely pleased for you to post the details of the company you used as I and others may wish to try them out seeing as your results, at least superficially, look quite good and traditionally blasting processes have been frowned upon for being destructive. Just as sanding is and yet I cause relatively little damage compared to others, if we as a community were to find a company that could offer a gentle stripping process that would be great, that includes me if you only knew how hard work stripping old timber by hand really is, spending less time stripping and more time finishing would be nirvana. Everything I do here Mike is to try and help people as I enjoy my job, historic houses and timber and have generally been brought u to be quite a helpful person. I learn constantly and never assume I always have the answer, I have AN answer which may or may not be better than anyone else's answer. Answers which are learnt from dedicated lifelong research and a lot of hands on experimentation. I am very careful to try and give people as much information as possible so they can make their own mind up, and preferably help them to narrow down their own areas of experimentation, which I encourage. 95% of the techniques I use were not part of any of the courses I attended and in fact I am not aware of them being on any syllabus as they are too obscure. Anyone can do what I do and better, they just need patience, practice and an open mind, all I try and do is give people a possible shortcut from all the mistakes and successes I have had over the years, that's all. Whilst I am always sorry if people get upset, I make no apologies for disseminating correct facts and correcting inaccuracies where I see them. As I said, I personally am very happy when I am proved wrong because it gives me the opportunity to learn something new, although I am aware others see it as a personal attack, which it isn't meant to be. Solid frozen CO2 at <-78 celsius density of 1.5 g/cm3 hits the surface at supersonic speeds, not gas as you say. This imparts considerable kinetic energy to the substrate and may not be suitable in all cases. Should I not correct your mistake? This forum isn't for just for one individual and their pride, it's for hundreds of people to try and support each other in the restoration and upkeep of period buildings and artefacts. Letting people know all the facts could possibly help others avoid unwanted damage. I am happy for people to judge me on my merits of trying to help . Best, T.

 

[88v8]

Still debating going with distemper for the entire ceiling....

Life Is short...
As I said before, my quick fix would be to paint the underside of the floorboards and do nothing with the beams.
Easy for me to say when I haven't seen them.

Distemper... distemper would do no harm. And would not materially add to the problems of anyone subsequently wishing to strip.

Ivor

 

[88v8]

There is a reason no blasting process is used by professional restorers for delicate work and cost isn't it as I said as any blasting is likely to be an order of magnitude quicker and therefore cheaper.

If someone developed the blasting equivalent of an air brush, oh, hang on, they did
https://www.guyson.co.uk/finishing-equipment/manual-blast-cabinets/micro-blasting-system-pencil-blaster
....fine etching of art and trophy glass, jewellery and watch repairs, cleaning fossils and other museum artefacts.... that sounds just the ticket, but how many people have one or will lug all the associated paraphernalia round to your house to clean the intricate bits of your woodwork at a price you'll want to pay....

I have done little detail stripping. A fireplace, oak, egg & dart, carving, painted. The paint had gone in the grain, in the carving.
Hot air gun & scraper, small blowlamp and chisel, carving tools, dental tools, needles. Many many hours.
And an oak window from the same source, easier as no carving but the paint had gone in the grain.
Should have used poultice I guess.

It depends so much on the operator. Used to have a classic car, the bonnet needed to be repaired and repainted. Took it to a company for plastic media blasting. Blast cleaning of car panels is or can be very harmful; the panels can heat up and distort into uselessness.
The bonnet came back perfect. Phew.
It depends on the operator and the correct choice of blasting medium, the pressure, the dwell time.

Can see the potential merit of dry ice. As Mike says, after hitting the surface, it sublimes into a gas, nothing to clear up.
I have a very grainy elm doorframe that wants stripping, in this neck of the woods the best I can find is soda blasting.

All blast/abrasive removal techniques are potentially damaging. I winced when I read Pineapple's post about a disc sander. Boy, can you do a lot of damage with a disc sander. How do I know that..........

Ivor

 

[Toby Newell]

Ivor is correct.

Any mechanical process is potentially damaging, it all depends on how much care you take and how large the 'bite' is.

If you take things to the logical extreme then removing one molecule at a time, in theory, you could remove an applied finish with almost zero damage to the substrate, which is why an air bush type micro blaster is potentially less damaging than a larger system that takes bigger bites each time.

On uneven surfaces like beams I use a selection of sharp and pointy things, including brushes of various materials, the same with chemical stripping, which still requires mechanical assistance at some stage. Unless the surface is relatively flat and has virtually no finish then sanding isn't the best first option, rather scraping, picking, brushing should be used to remove as much of the coating / dirt etc as possible and sanding with a finer grade abrasive only used really to give the surface a smoother ground for apply a new finish / oil / wax etc and remove any artefacts accidentally made with the aforementioned pointy things, which happens. Pound for pound for a finished smooth surface I would argue my method is probably the least destructive of all processes as blasting, of any sort, rarely leaves a smooth surface, it is usually a little fluffy, which is less durable, holds dust and obscures the beauty of the underlying wood, removing the fluff,guess what? takes abrasive processes whether that is gentle scraping or rubbing with an abrasive compound, which effectively are thousands of little scrapers.

As Ivor says, almost anyone can strip timber or any substrate for that matter with not an immodest amount of effort with fairly little damage. The problem is time, if you allow many months for a project this isn't an issue, if you are paying someone then stripping anything gently is going to cost more and this is where the conflict lies, getting the balance right. Stripping is a large percentage of my working life and if someone were to develop a truly universal, safe and gentle system that is reasonably portable I would potentially be in line as an early adopter.

My stripping box consists of three large attached lid containers. It contains no sanders, but several dozen brushes, which makes it look like I have an OCD problem.

 

[FamilyWiggs]

Crikey - that was quite a read.

We stripped an awful lot of layers of black/brown gunk from heavily varnished, plastered and painted beams that were hundreds of years old with the excellent Klingstrip products (Strippers of Sudbury) and a lot of elbow grease. Nothing more abrasive than a sponge scourer (not green ones!) and warm water to clean the beams after the stripper had done its work.

It took a long time, but the results are very good and nothing destructive has been achieved - which was important as there were some pretty friable parts. Afterwards we have just waxed the beams with some beeswax (with I think a little warm colour in it which is probably a heinous crime!)

I'm not an expert like Toby or Mike. I'm just trying to do the best by my house and undo some of the damage of previous owners (who knew not what they were doling but should still be cast into Dantean infernos for their actions).

Personally I would never sand a beam. If you can sent Klingstrip a sample of your gunk I think they can advise on what particular potion will work best for you.

 

[urowho]

I'm probably a psychopath (and wrong) but I'm itching to use a nail gun to nail a whole set of laths to your joists and plaster the whole ceiling with lime, the way it was probably originally designed! Then I'd paint it off white in clay paint.

 

[Abi Cott]

Based on my beams I'd just get someone to paint them in an oak effect in a lighter colour.
Mine are pitch pine approx 1829. The first coat of gunk on them is an oak effect finish. I've found it on quite a lot of the on my pitch pine timber in my house and adding something rather than subtracting it might be easier, less messy and more reversible.

If they are older than that and you never wish to restain or paint them. Kling strip. It's a three hand job to apply the cling film but otherwise a doddle to do. The problem comes if you want to paint them after when you need to jet wash them or the new paint peels (t shirt received) depending on the nature of your gunk try speaking to Strippers of Sudbury. But a poltice style stripper is well within DIY abilities (even mine) and only horribly messy rather that oh my god messy. Except if you don't wash it down enough your next layer of paint blows (t shirt recieved)

 

[skier-hughes]

I'm probably a psychopath (and wrong) but I'm itching to use a nail gun to nail a whole set of laths to your joists and plaster the whole ceiling with lime, the way it was probably originally designed! Then I'd paint it off white in clay paint.

I'm pretty sure it wasn't designed to have laths affixed with a nail gun :lol: :lol: :lol: :lol: :lol: