以PNP紙（press-n-peel blue transfer film）為保護層，進行金屬表面質地效果處理的蝕刻法，除了官方網站有詳細的使用方法介紹之外，在網路上也有許多金工創作者的P N P paper心得分享。
I have been checking the internet and trying to find if there is a possibility that I could transfer PNP image onto a curved surface. I have found nothing, but I have to have it - both the chance and the surface. The piece I am working on needs plenty of forging. If I etch→forge the piece, the patterns and textures would be changed, maybe even flattened or gone; if I forge→etch the piece, which is what I have done, I would have to find the answer to the question: how to transfer a PNP image onto a curved surface?
Therefore, I did some tests.
一般來說，PNP paper只能用於平坦的金屬表面上，因為它需要熱、壓才能有好品質的轉印，所以任何無法與PNP paper貼服的部份，都可能影響蝕刻圖案的效果。目前正在製作ing的此物件，我需要的圖案只能使用PNP paper進行轉印，才能滿足精細度的需求。然而先將圖案轉印到金屬上，在腐蝕之後再進行塑形，蝕刻的圖案很可能會在鍛敲的過程中扭曲變形，甚至凹陷；反之，如果各大小零件的形狀、尺寸、嵌接都定型之後才進行蝕刻，我要面臨的就是「PNP paper的圖案能否被轉印到彎曲的金屬表面上呢？」這個問題了。
Certainly I started with a clothes iron. Although the metal sheets were forged to metal bands, they still have smooth surfaces and the PNP papers seemed to be placed nicely on the surfaces.
However, the contact areas were far too small so the pressure and temperature were not enough and even, therefore, the images were not successfully transferred. The result was bad.
Then, I thought of using a hair dryer.
The result was even worse. The temperature and pressure were too low and weak, and not stable either: I applied the pressure with a steel ruler (flat side), and it caused the friction.
There are people using rub-on transfer stickers for the protection.... I did consider to order custom-made rub-on transfer stickers, and I made phone calls to the companies.... no way, they are ink-based images.... .
I placed the PNP images on the surfaces and fixed them with masking tape for the first try, and the result was.... not too bad, no burning masking tape, and the images were transferred quite nicely. But the masking tape stuck to the metal and left stains, which couldn't be removed by scratching - the transferred images would be off either.
一開始我用紙膠帶固定PNP paper。紙膠帶雖然不會燒起來，但是會烤得脆脆硬硬地，巴在金屬表面，要摳摳摳。一陣翻箱倒櫃，我翻出一卷磁鐵帶。PNP paper定位，拉緊，頭尾用磁鐵帶覆蓋、壓緊（並非為了磁性，是為貼服與加壓的效果），用金屬夾固定，送進烤箱，以200℃的溫度加熱......最少二十分鐘。件數增加，溫度也要拉長（比較保險）。
I found a magnetic tape. I placed the PNP images on the surfaces again, and covered them with the magnetic tape (for the protection, not the attraction), then hold them with metal clips. The oven temperature was set to 200℃ and baked for at least 20 minutes (longer time if more pieces), and it came out....
It might be working too with baking paper + binding wire. I presume.
ps. Do not quench the whole piece after baking, otherwise the PNP film could become crispy and crack up when peeling, which would cause more problems. Just leave it and let cool.