Post-Catalyzed Lacquer Cure Time
Curing reactions for post-catalyzed finishes do release smelly formaldehyde, and take longer at cooler temperatures. January 28, 2009
Question
We've started using post-cat as an upgrade from pre-cat lacquer. We recently installed cabinets in an occupied home and are getting flack from the owners as two-three weeks later the finish is still off-gassing. My rep says three days should be sufficient, so what's up? I love the hardness of the product but if you can't install for weeks after finishing I may have to switch back to pre-cat.
Forum Responses
(Finishing Forum)
From contributor G:
It has to be warm with good air movement for those three days or the crosslinking won't happen - until it gets into the customer's house, warms up and gasses off.
From the original questioner:
We've taken the doors back and are storing them in the back of the shop. This area is not heated currently. Do you mean that the cross-linking happens more slowly at lower temperatures or that it doesn't happen at all?
From contributor R:
Over catalyzation will cause a product to gas off longer than normal. If you can smell the coating yourself don’t release the project to your customer as it could cause legal issues. Some companies add a "scent" to their coatings so the gassing off isn’t as foul smelling as usual.
From contributor C:
We use post cat lacquer also. We've noticed it even inside boxes that have been closed up for several weeks after finishing. We spray boxes and doors separately, then after a day or two hang the doors on the boxes. Sometimes they will sit closed up in the shop for a week or two before installation. It's especially bad on something like a corner upper where we screw it to the upper next to it. Sticking your head into that box can even burn the eyes!
From contributor B:
As you describe, your eyes burn when you open a box. This is not a good thing for customers. Perhaps heat to speed the cure is the answer.
From contributor R:
Good air circulation is a must. I have a leaf blower I bought from WW Grainger to blow out the spray booth. I also use it to blow out the insides of cabinets that I’ve finished. At a steady blast of 80 MPH gail force wind it doesn’t take much time to un-stink a stinky cabinet.
From contributor R:
Some post catalyzed coatings are finicky and some; not so much. If in doubt, make it a point to check with the manufacturer. Another gremlin I have seen is that the sheen won’t be even throughout the course of the project. It is very important to be spot on with the amount of catalyst you add and it’s equally important to apply the coating in the temperature range given by the manufacturer.
From contributor F:
You have two things happening with your conversion lacquer. The first is the drying/off gassing. These are the solvents evaporating and most should be gone as your paint rep says. The other is the formaldehyde release from the resin crosslinking and hardening. That is the cause of the eye burning and quite possibly what the customer is complaining about. Heat will help speed up the crosslinking. Generally it needs to reach a BST (board surface temperature) of 125F to 140F for about a minute after flashoff. This will help speed up the formaldehyde release in your shop and not at your customers’ house. You will still get some release as it sometimes takes several months to get all the formaldehyde released. That is where the reorderant will help hide the smell.
From the original questioner:
To contributor F: Formaldehyde as in carcinogenic formaldehyde? Do you know if there is a significant difference in formaldehyde levels between post and pre-cat lacquer?
From contributor R:
Are you telling us that you don’t have a copy of the MSDS sheet for this coating? They’re easy to obtain from your coatings supplier. Either they can fax you a copy or mail you one. Once you have acquired one for each of the products you use, you can keep it in the same binder you keep your material usage log.
From contributor F:
To the original questioner: I don't know if there are different types of formaldehyde. What I can tell you from my experience as a technical sales rep of a major coatings manufacturer is that if you are using any type of coatings, and in particular an acid catalyzed product, you need a lot more ventilation than an open window and box fan. These products should be baked for maximum results.
I am aware you don't need to do this as the coatings will work on a slow dry schedule too but if you want to turn the product around fast and install in a customer’s home, you should be baking the finish.
I would have never sold a catalyzed finish to anyone not having an oven and proper ventilation. Look at what the manufacturer recommends for a drying schedule. The sales rep may say you can use it without baking or just let it air dry out in the open and of course, a lot of shops do just that. But it isn't what the product was designed to do. I'm not aware of any catalyzed product, post or pre that do not require baking. That's just my experience.
From contributor L:
I can shed a little light on the formaldehyde issue. This resin is either part of the formulation and is added by the manufacturer or occurs naturally as part of other raw materials that make up most post-catalyzed wood coatings. If your eyes are burning, there is at least some formaldehyde somewhere in the formula. Manufacturers are working hard to get away from this resin system for obvious reasons, and some offer formulations that do not have any formaldehyde resin that is added during manufacturing.
I would not worry too much about it though. You would need to be around it in its liquid form for quite some time before you would see any effects from exposure. Most coatings get their final cure after 30-40 days, but in enclosed areas (like inside the boxes) what is off-gassing could certainly hang around for a while longer. They should wait the 30 days and use Simple Green to clean the boxes.
If there are lights nearby, have the bulbs changed out too. It may seem farfetched but some of the off-gassing solvents/resins can actually adhere to the bulbs and when they are turned on and heat up, they will release the residue and make it seem like the cabinets are off gassing.
From contributor G:
While most cat lacquers will benefit from baking as those lucky enough to have a bake cycle automotive spray booth can attest, most bake enamels went out of vogue in the 90's. Crosslinking is quicker with more heat and won't happen (in many cases) without enough heat. For production-line type finishing, baking is essential to keep the line moving. For smaller shops, it is not vital.
