# Softening Kit Plastic



## Bluwtr (Feb 28, 2021)

I've mentioned in a few other of my posts about cheap kits. The last one that I'm working on is a farmhouse. I'm using Tamiya Extra Thin (green bottle) as my solvent/glue. I went with this because N-scale models are small and I'm not the most delicate of men! Because it is so thin it doesn't have a lot of contact time. Does anyone have suggestions to "pre-soften" the plastic? Like working with PVC pipe, using the primer cleans AND softens the plastic so that the solvent weld actually bonds and holds.

Just wondering if anyone has done this or have ideas.

Thanks,

Wes


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## 65446 (Sep 22, 2018)

Not understanding what the big prob is..
If you have a plastic kit it's likely polystyrene (certainly not delryn !) ..Why not use the glue made for this plastic where it is to be put (corners/ends/ledges) and put it together ?
N, HO, S, O, or your human size makes no diff..Why pre-soften kit components which potentially is going to warp/bend/deform them ?..
Again, add the glue where needed. Press the parts together. Hold them a few seconds, and fuggeddaboudit !


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## Bluwtr (Feb 28, 2021)

That's the issue. The cement I am using is so thin there is not enough time on this kit for the plastic actually melt together. It is a 3D kit that my wife ordered via Amazon. They are crap but I have them.


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## 65446 (Sep 22, 2018)

What "melt together" ? 
I have 2 walls joining at a corner. I put a bead of glue on one, press em together, and let em cure/dry while keeping em at a 90 Deg angle.. What's the prob ? The components aren't supposed to melt, anyway; just adhere to one another, fusing together somewhat while drying.


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## Bluwtr (Feb 28, 2021)

Many plastic kits are SOLVENT WELD. The glue actually melts the plastic together to form the bond. The glue is not the bonding agent --the solvent is. The solvent MELTS the plastic which flows together and basically crosslinks the polymer, then solvent evaporates leaving melted and fused plastic. Like I mentioned in my OP, just like PVC pipe. 3D prints used many different types of plastics. I have no idea which polymer was used in construction. My cement/solvent is very thin and evaporates before the plastic has time to join. I mentioned that I am using N scale because a huge glob of Testors glue etc. would look like garbage. This i why I like the Tamiya solvent cement--very thin so it doesn't leave solvent marks--that has ALWAYS been a bane/pet-peeve of mine with models even when I was a kid. I much prefer solvent-weld vs. standard model cements.


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## CTValleyRR (Jul 26, 2014)

I can't see Telltale's remarks, but it sounds like he's being his usual helpful self... totally missing the point and trying to tell you the way things work.

Many model cements these days are what you refer to as a solvent weld cement. It DOES matter what kind of plastic you're trying to glue, though, because solvent cements only work on a few different compounds. If the plastic isn't styrene, your solvent cement won't do anything.

Do a test. Take a piece of scrap ( like part of a sprue) and immerse it in a puddle of cement. It should basically dissolve. If it doesn't, the plastic used for the kit is incompatible with that kind of cement.

I will say that I model in HO, not N, and have never used Tamiya cements (or any of their products), but I have used Plastruct and Model Master (the stuff that comes in a square black container with a needle applicator), and have successfully glued some very small parts with both.

If you tend to be ham-handed in the application of adhesives, I have found these products to be helpful: Touch-N-Flow Applicator , 1 oz. Bellows Type Glue Applicator (Set of 2) , Extra Applicator Caps For Micro-Mark CA Bottles, Pkg. of 24 (despite saying "for Micromark CA Bottles", they fit a wide variety of adhesive tubes).


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## GeeTee (Dec 23, 2020)

Like when glue PCV Pipe, if your using a solvent based glue like MEK or Acetone , you want to first make sure the surface is clean and free of paint. Apply the solvent to both the surfaces with a paint brush ...wait about 60 seconds for the surfaces to soften ....then REAPPLY , once thats done put the parts together...Now comes the important part , you need to MOVE the two pieces relative to one another to get good inter mixing of the plastic , if you dont you wont get a good weld . This is especially true when using "straight solvent" with no filler in the glue. 

You do the exact same thing for PVC pipe , you prime it to remove any contaminates , then apply the glue , assemble , and TURN 1/4 -1/2 , No turn no weld ...Leak. PVC glue does have filler in it to help fill the gaps.

As CTValleyRR said make sure you using the right solvent.


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## 65446 (Sep 22, 2018)

CTValleyRR said:


> I can't see Telltale's remarks, but it sounds like he's being his usual helpful self... totally missing the point and trying to tell you the way things work.
> 
> Many model cements these days are what you refer to as a solvent weld cement. It DOES matter what kind of plastic you're trying to glue, though, because solvent cements only work on a few different compounds. If the plastic isn't styrene, your solvent cement won't do anything.
> 
> ...


You are saying the SAME THING I said, wise acher, except you go into tons of techno-bunk you don't need in order to put together a tiny little N scale plastic structure ! You are telling him to use different adhesives !! He's got a plastic kit his adhesive is not working for...I told him to use polystyrene glue... What do you mean you can't see my remarks !!? They're right there ! I'll bet you wouldn't say it to my face in a real MRR club room what you get away with calling me here !
This is a *H O B B Y*, not a business, as you treat it !! My input in it is as valid as anyone's !!
I offered the man help. That is all that is expected in a hobby club ! I was having a nice conversation with him until you showed up..You are the instigator, not I, you know-it-all twit, you !!


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## 65446 (Sep 22, 2018)

*BLuwtr *
Why do you assume the Testors glue has to be a 'huge glob' ? A few small dots spread with a toothpick will suffice to hold a model your not likely going to be handling much more after its on the layout. And if glue did stick out, how easy it'd be to juz slice/sand it off..
Whatever you come up with I wish you luck with it....


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## Lemonhawk (Sep 24, 2013)

I thought the best way was to hold the parts together then apply the cement and the cement flows itself into the joint. Always worked that way for me. Must be strange plastic if this does not work.


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## GeeTee (Dec 23, 2020)

Lemonhawk said:


> I thought the best way was to hold the parts together then apply the cement and the cement flows itself into the joint. Always worked that way for me. Must be strange plastic if this does not work.


that works with CA "glues" but not so much with solvent based . If you don't get good mixing between the parts you won't get a good weld. CA based "glues" just interlock the parts together , theres not much if any weld formed. Solvent based glues dissolve the plastic into a semi liquid state so the two parts can fuse together as a single part when the solvent evaporates.





Bluwtr said:


> Many plastic kits are SOLVENT WELD. The glue actually melts the plastic together to form the bond. The glue is not the bonding agent --the solvent is. The solvent MELTS the plastic which flows together and basically crosslinks the polymer, then solvent evaporates leaving melted and fused plastic. Like I mentioned in my OP, just like PVC pipe. 3D prints used many different types of plastics. I have no idea which polymer was used in construction. My cement/solvent is very thin and evaporates before the plastic has time to join. I mentioned that I am using N scale because a huge glob of Testors glue etc. would look like garbage. This i why I like the Tamiya solvent cement--very thin so it doesn't leave solvent marks--that has ALWAYS been a bane/pet-peeve of mine with models even when I was a kid. I much prefer solvent-weld vs. standard model cements.




_Just applying the solvent to a joint will accomplish little _, the solvent itself will keep the molecules of the pieces separated enough that almost no bonding will form ,* you have to have mixing* to get the adjacent molecules close enough to bond , adding styrene (Styrofoam ) to the solvent should help , because you have some free floating styrene molecules already mixed in with solvent. 

I agree solvent-weld is much better , It has much higher mechanical and thermal shock resistance , than CA or Epoxy.


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## CTValleyRR (Jul 26, 2014)

I hear what you're saying, but again, speaking of my experience in HO, I have never moved the pieces after applying cement, and have never had a bad joint. I usually clamp the parts and apply a bead of cement to the inside surface and remove the clamps after it has set (approximately 30 minutes).


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## MichaelE (Mar 7, 2018)

Lemonhawk said:


> I thought the best way was to hold the parts together then apply the cement and the cement flows itself into the joint. Always worked that way for me. Must be strange plastic if this does not work.


It still does and always has worked that way for me.


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## gunrunnerjohn (Nov 10, 2010)

Please dial back the animosity or I'll have to close the thread. Personal insults are not now, nor have they ever been allowed here.


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## vette-kid (May 2, 2020)

O have done a few 3d printed kits and find that the polystyrene glue due work, it just takes a little longer to set. I would try a different glue, sounds live this one is just to thin. Most of the time the glue didn't really leave much evidence when dry anyway. 

Sent from my SM-G781U using Tapatalk


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## Old_Hobo (Feb 20, 2014)

This is my all-time favourite cement for this hobby, as well as basic plastic model kit building…..just apply with the included brush…..

Hundreds of plastic train cars, model tanks and planes have held together for decades…


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## Old_Hobo (Feb 20, 2014)

telltale said:


> What do you mean you can't see my remarks !!? They're right there !


Just so you know, he has you on his ignore list….when you are on an ignore list, the person doesn’t see your comments in a thread, but can see everyone else’s…..

Personally, I don’t put anyone on an ignore list…..as you say, everyone is entitled to comment on any subject, and if I don’t agree with someone, I just agree to disagree…..


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## vette-kid (May 2, 2020)

Old_Hobo said:


> This is my all-time favourite cement for this hobby, as well as basic plastic model kit building…..just apply with the included brush…..
> 
> Hundreds of plastic train cars, model tanks and planes have held together for decades…
> 
> View attachment 561401


I've been using this one and I'm happy with it. Not sure if it's the same just different bottle?










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## Old_Hobo (Feb 20, 2014)

I do believe it’s the same glue, but I like the little brush that comes with the glass bottle version…..


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## Big Ed (Jun 16, 2009)

gunrunnerjohn said:


> Please dial back the animosity or I'll have to close the thread. Personal insults are not now, nor have they ever been allowed here.


Why close the thread?
Just yell at the instigator?
Not hard to see who it was.


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## 65446 (Sep 22, 2018)

Well, isn't that special !
I initially, in 2nd post, suggest *polystyrene* cement to the *OPer*, then get dissed for it by a member not even knowing I did, just because he or she has it out for me. Talk about animosity !
Later, others suggest Testors, too ! Maybe it's time for *MTF* to dismantle the 'I*gnore List*' feature.


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## gunrunnerjohn (Nov 10, 2010)

I think it's time to simply move on, there's no point in continuing to pick at this.


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## scenicsRme (Aug 19, 2020)

Now back to the original program, still in progress.
If you are working with home 3D printed kits or even some commercial kits there may be a film or surface coating on the plastic. When I was building plastic car kits for competition,the first thing I did was to soak all the sprue trees of parts except the plated ones, in a hot soapy water bath, hot enough that it was uncomfortable to my hand with a good amount of grease cutting dishwashing liquid like Dawn. Sloshed them around for a few minutes, then rinsed with warm water using the sink sprayer while the parts were in an Asian type rice colander (fine holes meant for rinsing rice) until there was not trace of soap rinsing off. I then placed them on a clean towel to dry.I used a solvent type glue that I had dissolved a small piece of clear sprue in the bottle to give it a little more body. I used a glass syringe with an 18 ga needle as an applicator. jigged the parts solidly in position using clamps, rubber bands, masking tape, or whatever worked to keep in alignment and tight contact, just be careful to keep tape away from seam so solvent didn't wick under it. I ran a thin line of the glue down the seam, judging the amount to be enough when it just appeared along the other side of the seam. I allowed it to set undisturbed for 1/2 to 1 hr. before unclamping. 
Note that some of the plastic fiaments used in extrusion 3D printers are not soluble in some solvents commonly used for liquid plastic cements. As suggested test some scrap to see if it dissolves. You may need to use a stronger/different solvent such as Acetone, or MEK (available in paint departments) or hexane (more difficult to find, sold as Bestest rubber cement thinner, try an art supply or online). If the scraps don't readily dissolve or at least get gooey/sticky after a few minutes it's not going to glue your plastic. Then you may have to resort to a CA for plastic or epoxy.


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## CTValleyRR (Jul 26, 2014)

OP hasn't been back in a while -- perhaps frustrated by the unhelpful tone of the early comments.


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## Bluwtr (Feb 28, 2021)

I decided to just let it go to rest. Turned into a pissing match which was NOT my point or intention. I may not have been clear in the beginning but I think all options and suggestions have been added.

I think we can put this to bed.

I'll think of another topic to start a fire storm and post that question in a day or two!


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## gunrunnerjohn (Nov 10, 2010)

Sounds like a good idea, I'll close this thread.


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