Refinishing Chairs Attacked by Cleaning Compound
Murphy's Oil Soap can degrade some of the less durable finishes. Here's advice on cleaning and refinishing. March 16, 2015
Question (WOODWEB Member) :
I have a question regarding using Murphy's Oil Soap on a pre-cat lacquer. I am re-finishing an entire restaurant full of the very sticky chairs. The chairs are made by Shaffer Commercial Seating, and are about 15 years old. A lot of the finish has rubbed off, and what remains is very tacky. You can use your finger nail and get to bare wood if you try hard enough. I refinished two chairs using pre-cat lacquer (dull rubbed) from Sherwin Williams. They have been in the store under normal use for about eight months, just to see how well the finish would hold up. They (the restaurant) were impressed enough to want the remaining chairs refinished. The original two chairs are already feeling a little tacky. They use Murphys on them every week as a cleaner. Is it possible that the oil soap will dissolve the lacquer over time? I know the question betrays my ignorance, so just chuckle away and let me know what you can.
Forum Responses
(Finishing Forum)
From contributor M:
I doubt it. However, I'd spray the rest of them with conversion varnish. It's more well behaved (in my experience), a lot more durable (generally speaking), and is only a negligible increase in price. That, and two coats of CV usually gives me the look and feel of three coats of pre-cat. I've refinished a good number of business/office chairs with MLC Krystal with great results.
From contributor C:
I couldn't find much on Murphys oil soap MSDS. I'd guess the gummy finish is a combination of oil soap residue and hand oils/hand lotion. I can't imagine oil soap attacking cured pre cat. I agree with Contributor M. Conversion varnish is way better in a commercial setting.
From contributor N:
Murphy's oil soap is 99% water. Water every week on lacquer is not good. I agree with the CV but tell them to use a different cleaner.
From Contributor J:
You did strip them I assume?
From Contributor S:
The chairs ought to be prepped with TSP and water. The gummy feel is softened finish. The finish softens and degrades from the constant use of Murphy's soap. I think this soap is made from potash, do in terms of its pH it's a little on the alkaline side of the spectrum. Now it's not even a year and your pre-cat is starting to soften - again, Murphy's. The restaurant would do better for their furniture to use Weiman's a Furniture Creme, an aerosol furniture polish. It does a great job cleaning and it leaves little residue, unlike a similar Oz Polish. And for you, Krystal is a lot more chemical resistant than pre-cat. You didn't name your pre-cat. Some pre-cats cure out close to that of many conversion varnishes and some are not much better than nitrocellulose lacquer in terms of durability.
From the original questioner:
Thanks for all the info I really do appreciate it. Yes I did go to bare wood. The pre-cat I am using is Sherwin-Williams T77-F38. I figure Contributor S’s remark regarding nitrocellulose is probably accurate. I will look into the conversion varnish to see what is available here. I assume I would need a sealer as well. What about stain? Would I need to change it as well?
From contributor M:
No, you should not need a sealer with CV, although they do make sealers for them. If you spray straight CV, you theoretically get a bit more durable of a finish, and you only have to buy one product. I never bother using sealers, I just find them unnecessary with CV. I don't know what stain you are using, but follow the can's instructions on curing time. I've sprayed CV over the top of nearly every commonly available stain (Minwax, Cabot, and of course the industrial companies as well). Since you're buying a Sherwin-Williams product, look into Sherwood V84F83. That's what we spray, it's a good product. Be sure to get the correct sheen you want, the V84F83 might be specifically "dull" sheen, but at least it gets you in the right category. Thin it with butyl acetate, probably don't need to thin it any more than 5-10%.
From contributor K:
Opt for the formaldehyde free formulation rather than the V84F83. It dries faster, sands easier, and is in fact self-sealing. The v84F83 is not self-sealing and is recommended to use T67F7 sealer prior to topcoat. (This requires not only having to purchase the sealer as well as the topcoat but you also need to buy two different catalysts - V21 and V26). The Formaldehyde Free is a very versatile product, leaps and bounds better than its predecessor, and also requires less catalyst.
From contributor M:
I beg to differ about the V84F83, I have sprayed thousands of kitchen doors with it self-sealing. It's not the absolute fastest curing CV I've ever sprayed, but it is just fine as a self-sealer. You most certainly do not need to buy a dedicated sanding sealer for V84F83. The only reason we don't spray the formaldehyde-free version is because it's not water white, unless that info has changed in the past few months.
From contributor M:
To the original poster, Contributor K's recommendation on the formaldehyde-free version is a good one, don't let my comments above distract from that. I've sprayed it in small amounts as a test, and it's a good product. The reason we don't use it is because we also clearcoat all of our white paints, and we must have the least yellowing possible, and our representative has assured us that the formaldehyde-free will yellow more than the V84F83. If it weren't for that, we'd probably be spraying it.
From contributor M:
The formaldehyde free has a slight amber tint to it. The catalyst itself also attributes to this, as it is a deep amber color. Not noticeable enough on 90% of our production to make a difference. I have not seen it yellow any more than when first sprayed however, so don’t take this as traditional yellowing. It’s just slightly yellow off the gun and will stay that way. I must concur that the V84F83 is clearer and is what we use on the other 10% where the slight discoloration really matters. For instance, when we topcoat pigmented CV.
