Hello,
I have a situation where I applied Squadron Green Putty to an area about 8mm square and 1mm-1.5mm deep and it dry for several hours before sanded it down. When I went to rescribe some panel lines near the repaired area the plastic was soft like it gets with plastic glue and the tool just sank into the plastic.
Am I not giving it enough time to dry?
Thanks, George
That’s a heafty amount of putty. Squadron putty has the same ingredients in it as liquid model glue. This helps the putty adhear to the plastic. You should give heavy applications 24-48 hours to dry and allow the plastic to herden again. Or, apply the outty in thinner light coats multiple times.
Hey Drew,
Thanks for the reply. So you think the plastic will get back to its normal state in a couple of days?
George
It might then again it might not. Several thin layers with ample time to cure between is best. Ever watch those reality TV programs such as American Hot Rod? You can get a whole lot of information as to how the body guys do it.
You might find yourself needed to remove what you did. You also might find that this huge gob just shrinks and cracks as it dries. A clean case of haste makes waste. Also why are you trying to trowel in so much filler? Better to fill the void with scrap plastic then use the putty as a means to fill the tiny imperfections and blend the work into a smooth finish.
If you were purchasing a restored car, would you want the restorer to use the same technique of globbing on the bondo? Guarantee the end results will not be the quality you are looking for. Just a thought.
Hello Hawkeye,
Live and learn. I have sanded the area down with 600 and it looks good other than some small pin holes I see under 10X magnification that I can fill with CA glue. I just hope the plastic will allow me to scribe on at normal hardness in a couple of days. Have you ever seen plastic not return to its normal state before? I will in the future cut plastic to fill in larger areas. The repair is on a plane fuselage where had a sunken in area by a sprue on the opposite side. I have done bondo work before on wood and metal and have had great success in filling in 1.5mm deep areas at one shot and thought the principle would be the same on plastic.
George
Great George, you’re on you way to being a better modeler…live and learn, that’s why we come to places like this.
Using bondo on the surfaces you mention are different…they don’t react negatively to it. Bondo desolves plastic…the more you apply the more distilates you have that softens the plastic.
If you used Bondo’s 2-part epoxy putty on deep depressions on wood and metal, you can use the same material on plastic too. We are not talking about solvent-based, red-colored Bondo Spot Glazing Putty, rather the smelly stuff in a can which is mixed with the cream hardener.
While Bondo epoxy putty does generate some heat while it sets, it dissipates quickly and doesn’t seem to affect plastic. You can glob it on thick and pare away the excess with a knife after it sets. If you have used it before on other mediums you are aware that it sands and feathers well.
I use Bondo epoxy putty quite often. Mix a quarter sized blob of putty with a pea-sized dab of hardener. Mix and apply. It sets quickly, often in as short a time as 15 minutes. This allows me to keep working rather than waiting overnight for solvent putties to evaporate. It sands well, feathers well, and takes paint well. It is also less expensive than many model-company labeled products. A pint can, which will last a year or more, is less than 10 dollars. Its available at most auto supply stores (Pep Boys, Auto Zone, O’Reillys, etc.). Extra hardener is also available separately
Yes. Unfortunately, you’ll just have to wait and see. Sometimes the solvents, if they are trapped in the plastic long enough, cause permanent changes in the polymer molecules of the plastice and they won’t cross-link properly.
Try putting the part in a “paint curing” box for a day. (That’s a large box with holes in the top and a lightbulb inside. A small fan blowing into the box is a good idea, too.)
I want to thank everyone for the replies. I have taken note.
George