Sticky Laser-cut Terrain

[Spooktalker]

Just received an order of laser-cut terrain from Multiverse Gaming and the kits look good, but the MDF is very sticky to the touch. It looks looks and feels the sticky substance is melted resin glue used to hold the wood particles in board form. I did a trial of cleaning a piece with rubbing alcohol and it worked for the surfaces, but was labor-intensive, and I can't think how I could clean all the cut sides.

First, is this normal for MDF? My experience with laser-cut stuff has been purely with plywood.

If it's normal, what to do about it? Dare I hope that a primer coat will solve it and when the paint is dry, the stickiness will be gone? Of course I can try it on an off-cut but always helps to hear about experiences first.

Third, and I probably should have thought of this before opening some kits in my room here, but I was reminded of the fact that MDF is made using formaldehyde. What are the safety-precautions for dealing with this stuff? I'm seriously considering a paint mask and gloves.

And can you link me to a guide that covers these things. I'm thinking someone must have made an essential resource covering these things but my searches haven't found one. I found some threads where people talk about sealing in advance (primer being the top choice, and hairspray and pva also mentioned), but they don't talk about the stickiness. I was surprised as my first thought was wow, the burned smell (which I knew to expect) but immediately my second thought was wow, these are really sticky.

[Fitz]

I suspect you're correct that the stickiness is the binding resin, which is, as you say, formaldehyde-based. It would be a good idea to wear gloves while handling it, as the resin can be an allergenic irritant.

Under normal circumstances, formaldehyde out-gassing from MDF is only a problem over a fair length of time, and then only if the environment is unventilated. A sealer takes care of that issue. How the melting of the resin might affect this I don't know, but best to err on the side of caution.

I would suggest a spirit-based sealing coat — automotive spray primer has worked well for me with laser-cut MDF. As well as being less likely to react poorly with the semi-melted resin, it has the added advantage of reducing the chance of warping if you then use water-based paints or glues over the top.

[Spooktalker]

Thanks for the advice, Fitz.

No one has first-hand experience with stickiness?

I guess I'll do a trial on a scrap, priming and seeing if stickiness remains. Need to emphasize again my strong surprise at stickiness not being front and center in conversations I've read and threads I found through searches.   If it turns out I need to wipe the parts down with rubbing alchohol my first big laser-cut project here may turn into the "never-again" sort of project.

[Damas]

I've picked up mdf kits from many different manufacturers, a lot of them have had that sticky feeling and sometimes left the brown resin on my fingers, about 30% of the kits.
I've generally left the kits spread open for a couple of days to reduce the smell of the burnt wood and then just applied paints as normal.  So far, no paint has flaked off or reacted and I have used car primer, brush on household tester pots and minature paints, mostly just using a house paint as the undercoat.

My wife has a reaction to formaldahyde and hasn't had any problems going into my hobby room but I do keep it well ventilated.

[Daeothar]

Interesting; I have never experienced anything like that, and I've handled quite a bit of MDF over time (most of it of the non-model kit variety I must add).

I wonder what triggers this then, as it's also the first time I've ever heard of it...

[Skyven]

I had this problem with a set of Multiverse Gaming's 'Tower Caps: Cooling Vents' at the end of last year. The stickyness didn't go away even after leaving the items out for several weeks. Worse, I found it completely impossible to glue together the items with either white wood glue or super glue.

Interesting to know that it wasn't an isolated case. Is mdf different in Poland compared to the rest of the world?

[Daeothar]

You'd think so, based on these stories and experiences.

I've had MDF kits from Australia, the UK and US, and I never experienced anything even remotely like it!

[Malebolgia]

No problems for me with Multiverse. A year ago I bought, assembled and painted a couple of sets. All went easily, even glueing parts on other types of buildings (like hardfoam and resin). I got these:

http://paintoholic.nl/images/scenery/pawnshop4.jpg
http://paintoholic.nl/images/scenery/dolly1.jpg
http://paintoholic.nl/images/scenery/gw1.jpg
http://paintoholic.nl/images/scenery/pallets_rolls.jpg

I really like them. Nice sets which are easy to assemble and paint.

[MagpieJono]

I've most certainly experienced the stickiness that you have described so you're not alone. I bought some barrels and boxes recently and they were really bad.

[Daeothar]

I've most certainly experienced the stickiness that you have described so you're not alone. I bought some barrels and boxes recently and they were really bad.

Manufacturer?

[MagpieJono]

Supreme Littleness.

[nic-e]

I've never had that before on any mdf kits. I've also never had it on any mdf boards used in the studio or in works.

One theory if that the mdf being used is sub par (believe it or not there are grades of mdf.It confused me immensely!) and the heat from the cutting process has caused the binding to melt or separate. I've had kits be a little bit tacky ,mostly where two sheets of mdf have been packed together for a while and the glues in them have become a bit stuck, but it's never been actually sticky to the touch.
The kits could also have been stored badly and consistent shifts in temperature have caused the binding to melt and settle repeatedly, leaving the surfaces tacky.

Are the kits warper at all? Would you say the wood is weaker or less rigid than other kits you've built?

[Damas]

I would definitely say that some mdf kits have been very soft and flexible and some have been very rigid with beautiful sharp edges.  The source/type of mdf could be the root cause.

[tin shed gamer]

This interesting topic.
I'm not the world's biggest fan of mdf kits. I see the as dollies rather than a finished model.I do own a few.
 
My personal observation is that This issue runs right across the whole mdf sector of the hobby. It's not limited to one type of cut or the complexity of the nets ,or simply the quality of the mdf.
As I've the Supreme Littleness boxes ,and barrels. All completely bone dry.
I also bought three kits from Sarissa at York last Sunday. I've only opened the one(streets of Rome temple.)and that's as tacky as hell.

Which leads me to question just how common this issue is? If it is common then why isn't it being addressed? But if there own quality control IS aware of this issue.Then why do they feel its acceptable to pass it on to its customers?
No matter which company you've purchased mdf from , Each frame is manually handled and packed. So there's no excuses.
Personally I've emailed to complain. I suggest you do the same. Because we'd all kick-off if we'd payed £35. For a figure and it was miscast. These issues are miscast's (for want of a better word)and unacceptable . It's time we treated them as such.
What use is a product that is potentially covered in a skin irritating compound and requires sealing on the frames before you even assemble.(otherwise you'd be handling the raw parts whilst constructing )
Metal ,resin,and plastic all require mould releasing agents . These can be washed off,as cleaning figures is part and parcel of getting a good bond for the paint.
Personally I'm not keen on trying to wash mdf in warm soapy water😉

[shadowbeast]

No, I have never had that happen to me. It definitely appears that there is something wrong with that MDF.