sanding down putty

Thanks for all the helpful tips! Sorry for the delay in response. Been dealing with some health issues.

                   Matt

I actually avoid sanding as much as possible and most of time all together when using squadron putty. Using the wing root as an example, apply as mentioned above using a thinned mixture of putty and diluted acetone (I used generic nail polish remover). Using tape is a good idea to minimize mess. I let the stuff dry for a minute or two, and then using a q-tip soaked with more nail polish remover, I wipe it over the putty to remove excess and smooth it into the seam. I usually go through 2 or 3 q-tips per seam.  After it dries a bit, if the putty shrinked too much, I'll just add more using the same technique.  This method allows you to fill seams in very difficult to sand areas and also eliminated sanding away details.  The only real drawback is that it will not address 'steps' between mating areas.

I use Squadron white putty without any problems, though that's not to say that I'm closed to trying other products-I'm tracking down the 3M Acryl blue, and I have tried 2-part automotive putty, too.

But Squadron works with relatively little effort for me.  I apply it to a seam with a flat toothpick, or with a dental spatula (which dental staff use to apply their putties to a tooth's surface).  Then I take a cotton swab dipped in acetone and wipe it across the puttied area, to remove the excess and to help make sure the seam has the putty in it.  That cuts down on the sanding.

I will also take a dab of the putty and put it in a well in my palette, then use an eyedropper to add drops of acetone and make a thicker version of Mr Surfacer, and apply that to the seam with a brush.   I haven't had any problem with either method.

The 2-part auto putty was a bit of a problem, because I didn't mix the putty and catalyst in the right proportions, so it didn't cure properly (the instructions are based on using the whole can; I was working with a thimbleful).

A very good tip was mentioned above, and that is to plan your build in such a way as to avoid causing bad seams, or to minimize them.  That goes hand-in-hand with reading the instructions carefully and examining the kit, to see if you can spot potential problems.

For example, in an aircraft kit with a 1-piece lower wing half, and upper wing halves, the instructions usually direct us to glue the upper halves to the lower wing piece, then glue the whole wing assembly to the fuselage.  But that often leads to seams along the upper surface join at the wing roots.

A way to avoid that seam is to attach the upper wing halves to the fuselage, then glue the lower wing to the fuselage and upper wings.  If anything, you might have seam work to fix, but on the underside, where it's generally less noticeable.  I used that technique on the Eduard 1/48 P-39Q, it worked really well.

 

Your methodology failed you. What I would have suggested doing is to glue in some sprue on the inside of the fuselage to cover the windows. Then very lightly start to fill the windows from the outside until you had it built up enough to fill the window openings.

Green Putty would have probably done the same thing. The Xylene is what gives the putty its bite, and it bit too hard. The more putty you apply the more concentration of Xylene. As the putty cures the Xylene vapors will attack the plastic, especially if it was trowelled on thick. Hence the reason one should apply any putty in very thin almost transparent layers. Let each cure then apply more. Models are delicate, novice modelers tend to think they are pouring a cement sidewalk when applying putty. It just makes the task more difficult and potentially causes more risk of damage.

Thx Phil_h The kit is a Airfix A300 and the plastic is on the soft side.  I really like Tamiya putty although its kinda of rare where I live, none of the LHS stock it.  I will try milliput/Tamiya on my next build

9x19mm wrote:

I applied from the inside of a fuselage to fill the windows and it ate the plastic really bad on the outside between the windows.

It's simply a case of your 3M Blue being too "hot" for the plastic. I would expect something similar from any brand of solvent-based filler, including Squadron's.

A general "rule of thumb" for solvent based dillers is not to apply a layer thicker than the adjcent plastic. If you have windows separated by a frame smaller than the window aperture, it will most likely melt it (the frame).

In this situation, a better option would be to use an epoxy type filler, such as Milliput or Tamiya Epoxy Putty. These putties (and other similar types) don't contain solvents which are unfriendly to styrene and have another advantage in not shrinking when they dry.

Not trying to hijack here but since I heard great stuff about 3m blue I sprung for a tube figured it would last awhile.  I applied from the inside of a fuselage to fill the windows and it ate the plastic really bad on the outside between the windows.  I could take a picture if that would help.  Its not ruined just will take alot more puttying to fix it.  Have you guys ever had that happen? 

The best way I have found to apply Squadron putty is:

• Mask off either side of the seam/area being filled, as closely as possible to minimise collateral damage
• Squeeze a small amount of putty onto a suitable palette
• Thin to a soupy consistency using liquid cement ot lacquer thinner
• Apply putty to area required using a paintbrush
• Fill to the level of the masking tape surrounding the area
• allow to dry before removing the tape

When done correctly you have a smooth, paper thin application of putty which will require minimal sanding as described above (ie. 400 grit and higher, used wet.)

Never apply putty directly from the tube - it's an instant mess. When I need a heavier application than the method above, I will squeeze a small bead onto the tip of an artists spatula and apply using that.

 

Once you do get your putty down to near perfect level, switch over to a polishing stick to work it further and better feather the edge. 

Several thin coats are better than one thick one.

Glazing compounds such as the 3M Acryl Blue does a much better job IMO.

The trick is to not have to use putties unless absolutely necessary. Here is a link to some tips.

First off, don't appy it too thick!

I use wet or dry sandpaper wet and start with 320 and then switch to 400 or 600 depending. 

I don't use that putty any longer as the 3M Acryl blue is far better and sands easier.