Does putty soften plastic?

[topher5150]

I used some strips of thin evergreen plastic to make some fender flares. I put a generous amount of Tamiya Basic Type Putty to make a chamfered edge.  Went to check on it tonight,  hoping to and it a bit, and the evergreen strips pretty soft.  Once it cuers more will the plastic stiffen back up?

[Ace-Garageguy]

One-part putties have acetone or other solvents in them to keep them pliable in the tube, spreadable, and to make them "bite" and stick to styrene.

So yes, they will soften thin styrene.

And yes, everything should stiffen back up when the stuff dries.

For heavy fills you're really better off using a 2-part catalyzed putty.

One-part putties dry by evaporation of the solvent, so they're prone to shrinking and/or cracking if used for heavy fills.

2-part putties dry by chemical interaction, and shrink very little.

 

[Old Buckaroo]

Bill is right on, I haven't liked the putty they sell for models as far back to the 1990's.  This is my go to putty for plastic, and to date Ive never had any trouble with it.  The only challenge was mixing a kidney bean size of putty with a seed bead size amount of hardener. I used it on the nose of this Daytona Charger, But in the past Ive used it thicker for molding flares as you are making.

 

[Rick L]

When using putty try applying it in thinner layers. This will allow the solvents in the putty to evaporate quicker without attacking the styrene too violently. When using polyester resin use the same process to allow cooler curing between coats to prevent warping.

[mcs1056]

12 hours ago, Old Buckaroo said:

Bill is right on, I haven't liked the putty they sell for models as far back to the 1990's.  This is my go to putty for plastic, and to date Ive never had any trouble with it.  The only challenge was mixing a kidney bean size of putty with a seed bead size amount of hardener. I used it on the nose of this Daytona Charger, But in the past Ive used it thicker for molding flares as you are making.

 

If you want that Bondo to go on more smoothly, add some fiberglass resin to the putty before you add the hardener. It doesn't take much resin, and in the right ratio, it goes on smooth and without bubbles. FG resin is completely compatible with Bondo. 

[SfanGoch]

Sorry to say; but, that's way too much c_rap around those fender flares. As was stated previously, Tamiya putty is solvent-based and can unnecessarily soften the Evergreen strips and the plastic to which they're attached. It requires too much sanding which could alter the final shape of the flares and surrounding plastic. One can use Magic-Sculpt two part epoxy putty as a filler around the flares. It's available in 16 colors to suit one's needs. It's water-soluble and you can smooth it with a dampened cloth or wet fingertip to obtain the proper shape.

[64SS350]

I've found the best solution (for me), when using automotive brand or other solvent based putty, is to use an automotive primer first, even just Dupli Color.

I've also started using Tamiya polyester putty. Two part, but plays nice with the plastic. Sands like other putties.

[Mike 1017]

The cheapest way and {IMO} the best way is to cut pieces off the tree, dissolve them in thinner and apply it.

Mike

[michelle]

i use foam clay putty ment for  use making cosplay props and costume bits  it is soft and pliable but gets nice and hard when dry  and is water soluble and air dries is sandable and can be primed and painted 

[NOBLNG]

Sprue goo works fine, but on a heavy application like that it would soften the original plastic greatly and take forever to harden up. I know because I did it on my ‘41 Plymouth fenders. I now prefer Milliput fine white for any heavier applications. It is two part, can be thinned with water and has no odour, cures quickly and sands beautifully.

[peteski]

1 hour ago, NOBLNG said:

Sprue goo works fine, but on a heavy application like that it would soften the original plastic greatly and take forever to harden up. I know because I did it on my ‘41 Plymouth fenders. I now prefer Milliput fine white for any heavier applications. It is two part, can be thinned with water and has no odour, cures quickly and sands beautifully.

Water? Is that some sort of new Milliput 2-part putty?

The older one I have is 2-part epoxy putty and it does not get along with water at all. Just like any other epoxy putties or adhesives - water and epoxy do not mix.

Well, you can use water on its surface to prevent it from sticking to things, but not to make thinner.

[Mark]

You don't, or at least shouldn't, use water to thin two-part putty.  If you do, it will shrink drastically as the water evaporates.

If you need to make the putty more pliable as you are applying it, just "roll" it really fast between your hands as you are blending it.  The warmer it is, the more pliable it will be when you are positioning it.  Water can of course be used to smooth it after it is applied, to reduce the amount of sanding needed later.

[NOBLNG]

4 hours ago, peteski said:

Water? Is that some sort of new Milliput 2-part putty?

The older one I have is 2-part epoxy putty and it does not get along with water at all. Just like any other epoxy putties or adhesives - water and epoxy do not mix.

Well, you can use water on its surface to prevent it from sticking to things, but not to make thinner.

 

3 hours ago, Mark said:

You don't, or at least shouldn't, use water to thin two-part putty.  If you do, it will shrink drastically as the water evaporates.

If you need to make the putty more pliable as you are applying it, just "roll" it really fast between your hands as you are blending it.  The warmer it is, the more pliable it will be when you are positioning it.  Water can of course be used to smooth it after it is applied, to reduce the amount of sanding needed later.

It works fine for me and I haven’t noticed any shrinkage. I don’t actually add water to it…I only have to wet my gloved fingers a bit to make a fairly substantial difference in consistency.

From Milliput’s website:

”At all stages from initial mixing to final setting Milliput responds to the use of water. To aid manipulation and avoid sticking, fingers and tools should be kept moistened with water. There are certain instances when work may be carried out in a gentle stream of water under a tap. To obtain a smooth finish, mould or apply Milliput and then immediately wipe and smooth gently with wet finger or with a fine textured moist cloth.”

https://www.milliput.com/howto.html

 

Edited March 20 by NOBLNG

[peteski]

32 minutes ago, NOBLNG said:

 

It works fine for me and I haven’t noticed any shrinkage. I don’t actually add water to it…I only have to wet my gloved fingers a bit to make a fairly substantial difference in consistency.

From Milliput’s website:

”At all stages from initial mixing to final setting Milliput responds to the use of water. To aid manipulation and avoid sticking, fingers and tools should be kept moistened with water. There are certain instances when work may be carried out in a gentle stream of water under a tap. To obtain a smooth finish, mould or apply Milliput and then immediately wipe and smooth gently with wet finger or with a fine textured moist cloth.”

https://www.milliput.com/howto.html

 

That is absolutely true!  Notice that I stated "Well, you can use water on its surface to prevent it from sticking to things, but not to make the mixture thinner. "  I sometimes even use saliva on my fingers to prevent the epoxy from sticking. Might be gross to some, but it works. After all saliva is mostly water.

But that was not what is not what you originally posted.  You mentioned "It is two part, can be thinned with water".  That to me clearly means that you mixed the water into the putty mixture to make it softer/thinner, no?  I'll say again: epoxy and water to not mix.

[Matt87]

7 hours ago, michelle said:

i use foam clay putty ment for  use making cosplay props and costume bits  it is soft and pliable but gets nice and hard when dry  and is water soluble and air dries is sandable and can be primed and painted 

I like Tamiya white putty for filling in.

[NOBLNG]

4 hours ago, peteski said:

That is absolutely true!  Notice that I stated "Well, you can use water on its surface to prevent it from sticking to things, but not to make the mixture thinner. "  I sometimes even use saliva on my fingers to prevent the epoxy from sticking. Might be gross to some, but it works. After all saliva is mostly water.

But that was not what is not what you originally posted.  You mentioned "It is two part, can be thinned with water".  That to me clearly means that you mixed the water into the putty mixture to make it softer/thinner, no?  I'll say again: epoxy and water to not mix.

Well adding whatever amount of water that sticks to a finger dipped into water ( 1/2-1 drop?) does change the consistency of a marble sized wad and makes it a lot “mushier”, so I would have to say it can be thinned with water. Perhaps it does shrink slightly…but not noticeably so. Just my experience.

[peteski]

8 minutes ago, NOBLNG said:

Well adding whatever amount of water that sticks to a finger dipped into water ( 1/2-1 drop?) does change the consistency of a marble sized wad and makes it a lot “mushier”, so I would have to say it can be thinned with water. Perhaps it does shrink slightly…but not noticeably so. Just my experience.

Is it the added water or the heat from your fingers making it softer?  Hey, but the important thing is that it works for you.

[NOBLNG]

Definitely not the heat. I can knead it for a long time and the instant I add touch of water it goes soft and mushy. Further kneading dries it back out but it remains softer than before. Maybe only the Fine White reacts like this? I also have some Tamiya epoxy putty and it does NOT mix with water or react the same way. I do prefer the Milliput.

[Belugawrx]

8 hours ago, NOBLNG said:

Well adding whatever amount of water that sticks to a finger dipped into water ( 1/2-1 drop?) does change the consistency of a marble sized wad and makes it a lot “mushier”, so I would have to say it can be thinned with water. Perhaps it does shrink slightly…but not noticeably so. Just my experience.

I have had the same experience while contouring wheel arch flares with Milliput Super Fine White, water does help it smooth out and softens it quite a bit, very easy to feather out...don't know what's in it, but it works 

Edited March 21 by Belugawrx
corrected