MUST I Strip The Old Paint/Decals Before I Repaint A Diesel?

Kinda funny......I just painted 2 WbB Conrail units to CSX!!!! With the paint in good condition I just removed the Conrail logos and numbers with ultrra fine sandpaper, primed with Dupli-color gray primer SEALER and painted the colors with Tamiya spray cans. The 3 color paint may give you issues and I have not repainted any modern Lionel myself. Not real hard answers for you! I might try w/o stripping them. good luck!

Do what AMCDave suggested.  I have never repainted any model trains but I have repainted military models without stripping the old paint.  I didn't even remove the decals.  I did spray a gray primer first from a spray can.  Then I applied the final color.  Several thin coats (as thin as you can get with a spray can).  Then sealed everything with dull coat.  Worked ok for me.  Even if it doesn't work out and you have to strip it, you were going to strip it anyway.

Rick

Strip the old paint off and prime it, then paint. That's the only proper way to do it. When people don't strip it first you generally can see the old numbers and logos, along with paint lines underneath. Another reason is depending on what paint you use, its possible to have the new paint attack the old paint and you will quickly have a wrinkled mess on your hands.

Rob

Would also imagine that you will lose a lot of sharper detail like panel lines etc due to paint build-up from so many coats!

I've done it two ways. Complete strip and just remove the lettering. The latter works just as well as a complete strip. It will be easier to remove the shell rather than mask it off. The paint itself is a good primer. If you do decide to strip the shell then walnut shells or soda blasting is the safest way. Modern paint is difficult to strip with harmless chemicals like laundry detergent and fluids like alcohol and brake fluid can damage certain plastics. Unless you know what exactly you are dealing with its not worth the risk.

Pete

Soda Blast?  Do you mean baking soda?

Well.....about a 50/50 split. Think of it this way. I've done both......in my HO days I always stripped as detail is lost under lots of paint. BUT...O is a little different. Logos and letters can't show through if you remove them as I advised. And the Dupli-color PRIMER SEALER does just that.....seals colors etc so you can repaint.

It boils down to my other hobby classic cars. If you want a 100 point show car.....strip 100% of the paint and prep it like new. Want a good daily driver just make sure you have a solid foundation for your paint. My show winning Javelin still has it's 'Fawn' paint under it's current Big Bad Orange for almost 20 years......good prep is all it takes.

I am not a pro painter, but I do acceptable work.  I rarely strip if the existing paint is solid.  I do sand decal and lettering edges with #600 and water.  I always prime white when spraying yellow.  

My Goodness!!! While you're at it, just buy a can of paint and a 2" paint brush and go to town... Or better yet, buy yourself a gallon of paint. Dip it in and let it drip-dry, just like Lionel did in the olden days. Run your trains with the room lights low or out and no one will know.

On a serious note: Do yourself (and maybe others) a favour and do it correctly. I'm sure others will agree that compliments on your work is the best reward. And makes all the extra effort worth while.

I tried painting some boxcars without totally stripping them, then I stripped the new paint and did it again.

I'm with the majority, best to strip it.

I just redid two intermodal containers from the origonal "popsicle" livery to early REA and late CB&Q{someone had to do it } and I found the "popsicle" logos were slightly raised...had to take a Q-tip with lacquer thinner and remove them, then the body was smooth.

The amount of detail your willing to work for is the deciding factor on whether or not to strip and how to strip. Thinned airbrush modeling paint vs thicker auto motive rattle cans makes a difference too. I feather decal edge lines with fine paper, scuff sand with green scotchbright part of a dish sponge till I see no shine, clean with a MILD solvent, dust details and corners with a clean brush, spray light coat of sealer primer(which is more likely not to allow a reaction between any paints), dry well, LIGHTLY scuff and dust again, topcoat.  Save lacquer paints for metal or wood. Beware of lacquer thinner/acetone on plastic, or lacquer paint over other paints/plastic, they eat everything if over exposed, very "hot". But as Bob pointed out with skill, and care, they can be  used. When top coating without primer, sticking to a thicker but softer "plastic" enamel paint helps to avoid "pulls" & "crackles" in the under coat.

I am also with the majority. All that mask costs money, removing the shell costs nothing. A gallon of Purple Power costs less than all that extra paint to prime. It's non-toxic, will completely remove all the paint in 1 - 3 days. Sumerge it in a dish pan or small wash tub; you won't harm them.  Use an old tooth brush to encourage the crevices.  Rinse in clear water, shake it and let it air dry.

I forgot about using the purple degreasers to remove paint. Ive used it on models before never a train. I used the Castrol stuff, my fingers, a popsicle stick and toothpicks to push the loose paint off  

Is Purple Power OK for Removing Paint/Rust from Tinplate without any damage to the Tinplate?

I'm sure it won't damage the tinplate.  I don't know how good it is at removing rust, for rust I use Evapo-Rust, great stuff to remove rust.

Thanks John,

I am assuming that evapo-rust not available from local distributors and just internet orders?

Would be nice to pick some up locally if possible...

Cleaners like laundry detergent, Simple Green, etc usually have a high Ph and can etch metal. Maybe not enough to cause serious damage if you wash it away as soon as the paint is loose but why take the risk. Solvent strippers like Strip Eeze work much faster and won't damage metal. As for the rust, some 600 wet or dry sandpaper would remove the rust and smooth the surface at the same time. You will want to use sanding primer if the rust pits are deep though to fill them in.

Pete

You can get it all over.  I happened to get mine at PepBoys because they had the gallon size, but HomeDepot, Lowes, etc. all have it as well.

Pete, I doubt you can get rid of all the rust as easily as Evapo-Rust, the stuff is truly amazing for rust.  Note that it's only for removing rust, it has no other function.  However, it hasn't affected any plastic or other material I've immersed in it.

Question for "Adriatic"

What's the difference between enamel paint and lacquer paint? Aren't both a petro-distillate based paint? I'm assuming both will attack plastic without a primer coat.

Does anyone use acrylic paint with any success? I've tried acrylic, but have had a terrible time thinning it for air brush use.

Thanks John, I had just gone to the link you provided and since they didn't have where you can get it locally, I was bummed out having to order it.

I definitely would get rid of decals and printed/stamped letters - they show through.  In many cases I sand with #320 and #600 well to remove them and then prime and repait from there. 

Dennis,

You can also get it at Harbor Freight on Route 22.

Great, they have a 20% off coupon if I spend $100, so give me a reason to spend money!

I blasted this shell with baking soda to remove the lettering, logos, and numbers.

It's delicate enough to even blast the window frames without doing any damage to them. Then I wash it with soap and water, rinse with isopropyl alcohol and it's ready to be primed.

I prefer acrylic paints over the rattle cans. I buy "Acrylic Thinner" from my hobby shop. Don't use tap or distilled water. You will have better results if you use a dual stage airbrush as acrylic paints flow like no other when properly thinned.

I find it much easier to match prewar (and postwar) paint colors using acrylics. All it takes is practice, practice and a little more practice.

What kind of soda blasters are you using?

Testor's PolyScale ELO (EZLiftOff) works well for removing most of the lettering/marks on the model.  It doesn't matter whether they are painted on or decals.  If you are careful you can lift the markings with minimum damage to the base coat.  Most of the hobby base paints are now electrostatic-ally applied and are often urethane based.  They aren't coming off easily with chemical strippers.  You can "blast" them off.  If you're good at it, you can strip it down with minimal surface damage.

Regarding painting over the existing paint.  Unless you know what the paint you are coating is made of you can't be sure that the new paint won't react badly.  In general less aggressive solvents can be applied over coatings that were applied with more aggressive ones.  e.g. water based could be applied over enamel which was applied over lacquer.  This isn't always true and you should test on an inconspicuous area before trying "the real thing".

Regarding "sand paper".  I switched to plastic film based material which I wet sand with a drop of detergent.  For paint removal/finishing I START with 600 grit and move up to 800, 1000, 1200, 2000.  Anything lower than 600 is going to remove more than just the paint.  I've found it to be pretty rare that I can overcoat an old paint job UNLESS the original was all one color and that color was something neutral like white/off white or lighter shades of gray.

Lacquer penetrates and dissolves  things quicker than most enamel carriers, applying very thin coats which can dry very quickly and/or protecting the plastic with a layer of primer are necessary. I never use lacquer on plastic but have seen it done. On the other hand I have done many plastic model paint jobs with rattle can automotive enamels with 99% success, no primer. Just how "hot" is lacquer?, 30yrs ago I painted a vw bug with cherry red, 2 part automotive enamel, the spray gun never got cleaned. Two years ago I needed it, filled it with lacquer thinner soaked 48 hours, cleaned it out with a brass brush and sprayed my dune buggy a dirty mustard yellow. If not for its evaporation rate it would make an excellent paint stripper for metal. I do soak small metal parts in it to remove paint often.  Layer penetration, hardness, and shrinkage caused by evaporation and paint trying to lay flat, cause an increase in the "pull" of the surface tension of the topcoat on the bottom coat now weakened by penetration. As it dries that causes the cracking and pulling of a bad paint job. Like stretching electrical tape then applied over a softer flat sheet of kitchen plastic wrap. As the tape shrinks it pulls and crumples the softer plastic wrap under it. The only things Ive used that are stronger are methyl ethyl keytone based products that strip skin in minutes and are highly cancerous.

Adriatic,

Thanks for the explanation,,,think I will leave the lacquers for the pro's.

Happy Pappy,

Thanks for the acrylic thinner "tip". I have been using distilled water as a thinner for acrylics...maybe that's part of my viscosity problem.

My "surface protection" application experience is broad, auto, residential, industrial, art, modeling, etc., but not always highly in depth, lots of experimenting "cause it was there", lots of luck, tech by word of mouth. My acrylic paint use is kind of limited to detail brush work, because they flow! But seem to soft and spongy for my spray tastes, and my first "dabble" was one of my only "nightmare paintjobs"  so I avoid it in spray ever since. Plus, I am always scratching or chipping something, unless it belongs to someone else, so I prefer thinner harder paints when I can use them. Maybe proper thinning would have helped me, but I just stuck with what I knew.

 Mostly, I run old-n-dirty, battle scarred P-war (natural weathering) so I have only repainted a few really bad old trains, one plastic 0-4-0 dockside, a cast semi-gg1, and a Marx tinplate C. Van. found buried an inch down in a dirt floor(runs fine, plating and cars paint were perfect, but not the engine body paint. ). I played with the canned "plastic binding" paints recently, it was awful, one so thick it could almost wipe out box car rivets in one coat, but great pigment count, definitely a lawn and garden winner. The other, water based, very thin and runny, days to full cure, low pigment count, I almost cried trying to use it. Stuff even fisheyes on layers of itself, sanded or not.      

The 50K' view.

There is acrylic latex, acrylic lacquer and acrylic enamel and even acrylic urethane (amongst many others)coatings.  Acrylic is the part of the resin used to hold the pigment.  The other part of the resin includes the vehicle/volatile is used to "thin" the resin to flow and adhere to the surface.  With Enamels and Urethanes it's called reducer instead of thinner. 

Lacquer is one of the oldest resins known for painting.  It requires tough thinner which today is made up of similar chemicals used to manufacture many plastics.  Anything styrene included.  If you take solid styrene and put is in a container of lacquer thinner it will completely melt.  OBTW, that melted styrene is the best filler you can find for plastic models but is dangerous and difficult to use.  Microscale used to make a filler/putty made this way - I think it was called Microputty -  and it was THE best. Today serious modelers take styrene sprues and put them in liquid plastic welders to make their own.  Styrene welders are very similar to lacquer thinner.

On the other hand many reducers do not interact with substrates, they are there to only react with the paint and in some cases do not evaporate at all to dry the paint but react with it to cure the paint. Water based paints contain ammonia, or other amines, which makes the water evaporate faster and also are a go between water and the acrylic resin. 

Acrylic enamels will never completely dry/cure without heat because some reducer is trapped between the outer surface and the substrate so the reaction does not complete.  This is why Scalecoat I has to be baked and therefore is not appropriate for plastics.

Cured paint is actually tougher than any dried paint like lacquer because once the curing is complete the film is stable throughout.

A lot of rattle can paint these days are label enamel, Krylon for example, but have a very aggressive thinner and will lift a lot of paints. I have never had this problem with automotive enamels including acrylic and urethane based enamels. If a paint calls for mineral spirits or reducer as a thinner then its usually pretty safe over most finishes.

Pete

Ok so we need a few definite answers

• For stripping paint:
• • Soda Blaster or Purple Power
  • Remove windows or not
  • with the soda blaster, get a booth?
• Air Brush
• • Paasche or Badger
  • Double Action, Internal?
  • Paint
  • • brand
    • enamel or acrylic
    • preparation for air brushng (thinning?)

Thanks for all the feedback advice

Whenever possible remove windows or any clear plastic/glass before stripping and do not re install till you are done painting.

Use whatver works for you as far as removing old finishes.  Different materials react differently to physical or chemical processes.  If you decide to "blast" old paint off you need a booth and a good respirator.  If you use chemical strippers use protective skin and/or breathing gear.

air brush types and brands are very subjective.  Single action is easier to use/care for.  Double action more flexible (and more expensive).  You need to practice a lot to get proficient and the number one rule with an airbrush is to keep it clean.

Buy paint you like to use and works for you.  Only buy what you need and do not get too attached to left overs.  You can keep some of it around for brush work.  Paint will start to deteriorate in the bottle/can once its been opened. After a certain point ther isn't much you can do with the dregs and if you try to spray it you will clog the airbrush and waste more time cleaning than you saved by trying to use it.

Safety meeting for the day. I had posted this a few years ago, part of an airbrush tread.   The material used for painting and paint removal need safety precautions.  All would have an associated MSDS.  Material Safety Data Sheet. Surprisingly Water clean-up acrylic paints, cleaners, and thinners can be issues.  I eventually purchased an organic cartridge respirator.  Eye protection is also a good thing.  Noted that I usually felt better at the end of the day. 

This was added as part of the safety discussion.

quote:

Originally posted by OntarioRailFan: I've got a good paint booth vented directly outside. I also use ONLY water based paint.  Though I have not used a respirator.  Is this something I should add before I start my next round of painting????

YES From my shelf, what is written on the bottles.

Badger Modelflex acrylic paint  Non-toxic. Keep out of the reach of children. If ingested do not induce vomiting. Call a physician immediately.

Polyscale acrylic model RR paint Non-toxic. Contains Isobutanol and DPNB. Causes eye irritation. Avoid eye contact.  First Aid: For eye contact flush immediately with plenty of water. Not intended for use by children

Polyscale acrylic thinner  No caution listed.

Polyscale acrylic cleaner  May irritate eyes Do not get in eyes. Do not take internally. Close container after each use. Keep out of reach of children.  First aid treatment : Contains gylcol ethers. If swallowed call a physician or poison control center immediately.  In case of eye contact, flush with plenty of water.

Weaver ScalecoatI Paint Danger Flammable Harmful or fatal if swallowed vapor harmful Read addional caution on back of label. Contains Zylene, Benzene, Butanone Oxime, and Petroleum Distillates that may be harmful if misused. Read caution on individual containers carefully. Harmful or fatal if swallowed. If swallowed do not induce vomiting. Call Physician immediately. Vapor harmful, May be harmful by breathing vapor. Use proper ventilation. When using,do not eat, drink, or smoke. Wash hands immediately after use. Avoid skin contact.  Keep container tightly closed when not in use. Do not use on interior surfaces. For use on model train cars and hobby related models only. FIRST AID: In case of eye contact thoroughly flush with water for 15 minutes and get medical attention.  For skin contact wash thoroughly with soap and water. In case of respiratory difficulty, provide fresh air and call physician. Call 1 800 424 9300 for more health information FLAMABLE: Keep away from heat, sparks, and open flame. WARNING This product contains chemicals known to the State of Californina to cause cancer and birth defects or other reproductive harm. KEEP OUT OF THE REACH OF CHILDREN.  (Ya, that's all on that one ounce bottle of paint).

Floquil Railroad Colors For Emergency Health Information call 1 800 962 1253. Contains petroleum distillates. Vapor Harmful Keep away from heat, sparks and open flame. Causes eye and skin irritation. To avoid breathin vapors and spray mist, open windows and doors to ensure fresh aire entry during application and drying. If you experience eye watering, headaches, or dizziness, increase fresh air or wear respiratory protection. Close container after each use. Avoid contact with eyes and skin. USE WITH ADEQUATE VENTILATION. WARNING this product contains chemicals know to the State of California to cause cancer and birth defects or other reproductive harm. FIRST AID: If swallowed. Do not induce vomiting. Call physcian immediately. KEEP OUT OF REACH OF CHILDREN. 

Floquil air brush thinner CONTENTS AND FUMES MAY CATCH FIRE. CONTENTS HARMFUL. MAY IRRITATE EYES AND SKIN. KEEP OUT OF REACH OF CHILDREN.  Vapors may ignite explosively. vapors harmful. May affect the brain and nervous system. causing dizziness, headache, or nausea. Causes eye, skin, nose, and throat irritation. Keep away from heat and flame. Avoid eye contact. Avoid breathing vapors and spray mist. Use only in well-ventilated area. Wash thoroughly after handling. Intentional misuse by deliberate concentrating and inhaling the contents may be harmful or fatal. FIRST AID: Contains petroleum distillates and n-propoxypropanol. In case of eye contact, flush with plenty of water for 15 minutes. If swallowd call physician ofr Poison Control Center immediately. If inhaled, seek fresh air. If on skin, rinse well with water. There are a lot of other chemicals on the shelf. All with some kind of a caution. IMO At the bare minimum even using acrylic, water clean up, paints adequate ventalition should be provided. This was part of a larger discussion at the time that moved toward full face protection,(eyes),and a filtering system that pulls or inhibits breathing any of the chemicals present.  There has also been several threads on model spray paint booths. Spray Booth currently on the 2 Rail Forum.    Mike

Respirator from a local auto parts or body shop paint supply.  Note that the two cartridges are designed to be replaced periodically.  $30 to $50 maybe ????